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    "# Preview\n",
    "\n",
    "- Use these questions before class to check your familiarity with the chapter glossary and core terms.\n",
    "- Sign in from the account menu before you start answering the questions.\n",
    "- Multiple submissions are allowed. The highest score is kept.\n",
    "\n",
    "Review the [Chapter 10 glossary](../1000-two-samples.ipynb) before class. These ten questions mix multiple-choice and true/false: seven recognize terms and three connect related ideas. No calculations or code tracing are required.\n"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "ch08-preview-quiz",
   "metadata": {},
   "source": [
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    ".ch10-preview-feedback.correct { color: #1a7f37; }\n",
    ".ch10-preview-feedback.incorrect { color: #cf222e; }\n",
    "</style>\n",
    "\n",
    "<div class='ch10-preview-quiz' id='ch10-preview-quiz' data-question-set-version='dsm-ch10-preview-2026-10-19-v2'>\n",
    "  <p>Earlier submissions and best scores are retained. If you already completed this Preview, you do not need to repeat it; you may retry the revised questions.</p>\n",
    "  <div id='ch10-preview-questions'></div>\n",
    "  <div class='ch10-preview-actions'>\n",
    "    <button type='button' id='ch10-preview-submit' disabled>Submit</button>\n",
    "    <button type='button' class='secondary' id='ch10-preview-reset'>Reset</button>\n",
    "    <span class='ch10-preview-result' id='ch10-preview-result' aria-live='polite'></span>\n",
    "  </div>\n",
    "</div>\n",
    "\n",
    "<script>\n",
    "(function () {\n",
    "  var quizId = 'ch10-preview';\n",
    "  var questionSetVersion = 'dsm-ch10-preview-2026-10-19-v2';\n",
    "  var answersUnlocked = false;\n",
    "  var attemptState = null;\n",
    "  var stateQueue = Promise.resolve();\n",
    "\n",
    "  function stateRequest(action, extra) {\n",
    "    return fetch('/api/v1/preview-options.php', {\n",
    "      method: 'POST', credentials: 'same-origin',\n",
    "      headers: { 'Content-Type': 'application/json' },\n",
    "      body: JSON.stringify(Object.assign({\n",
    "        assignment_id: quizId, version: questionSetVersion, action: action,\n",
    "        page: window.location.pathname.replace(/^\\/+/, '').replace(/\\.html$/, ''),\n",
    "        questions: authoredQuestions, legacy_questions: legacyQuestions, legacy_version: legacyVersion, token: attemptState && attemptState.token,\n",
    "        revision: attemptState && attemptState.revision\n",
    "      }, extra || {}))\n",
    "    }).then(function (response) {\n",
    "      return response.json().then(function (payload) {\n",
    "        if (!response.ok || !payload.ok) throw new Error(payload.error || 'Could not save Preview state.');\n",
    "        attemptState = payload.state;\n",
    "        return payload;\n",
    "      });\n",
    "    });\n",
    "  }\n",
    "\n",
    "  function draftAnswers(quiz) {\n",
    "    var answers = {};\n",
    "    questions.forEach(function (question) {\n",
    "      var input = quiz.querySelector('input[name=' + question.id + ']:checked');\n",
    "      if (input) answers[question.id] = input.value;\n",
    "    });\n",
    "    return answers;\n",
    "  }\n",
    "\n",
    "  function saveAnswers(quiz) {\n",
    "    var answers = draftAnswers(quiz);\n",
    "    stateQueue = stateQueue.catch(function () {}).then(function () {\n",
    "      return stateRequest('save', { answers: answers });\n",
    "    });\n",
    "    return stateQueue;\n",
    "  }\n",
    "  var questions = [\n",
    "  {\n",
    "    \"format\": \"true_false\",\n",
    "    \"prompt\": \"True or false: Random assignment places study participants into conditions by chance.\",\n",
    "    \"concepts\": [\n",
    "      \"Random assignment\",\n",
    "      \"Random sampling\"\n",
    "    ],\n",
    "    \"explanation\": \"True. Random assignment determines which condition each participant receives. Random sampling instead determines who is selected from a population. The two random processes serve different purposes.\",\n",
    "    \"retry_hint\": \"Distinguish choosing participants from allocating participants to conditions.\",\n",
    "    \"id\": \"q1\",\n",
    "    \"cognitive_level\": \"recognition\",\n",
    "    \"reading\": \"../1003-causality.html\",\n",
    "    \"choices\": {\n",
    "      \"A\": \"True\",\n",
    "      \"B\": \"False\"\n",
    "    }\n",
    "  },\n",
    "  {\n",
    "    \"format\": \"multiple_choice\",\n",
    "    \"prompt\": \"A company randomly assigns customers to two checkout versions and compares completion rates. What kind of study is this?\",\n",
    "    \"concepts\": [\n",
    "      \"A/B test\",\n",
    "      \"Business experiment\"\n",
    "    ],\n",
    "    \"explanation\": \"An A/B test is a randomized comparison of two conditions or versions. Random allocation distinguishes this experiment from simply comparing customers who chose different versions for themselves.\",\n",
    "    \"retry_hint\": \"Look for both a comparison of versions and the way customers enter the groups.\",\n",
    "    \"id\": \"q2\",\n",
    "    \"cognitive_level\": \"recognition\",\n",
    "    \"reading\": \"../1001-ab-testing.html\",\n",
    "    \"choices\": {\n",
    "      \"A\": \"A/B test\",\n",
    "      \"B\": \"A comparison based only on customer preference\",\n",
    "      \"C\": \"A census of every customer\",\n",
    "      \"D\": \"A study with no measured outcome\"\n",
    "    }\n",
    "  },\n",
    "  {\n",
    "    \"format\": \"true_false\",\n",
    "    \"prompt\": \"True or false: The treatment group is the group that receives the baseline condition instead of the new intervention.\",\n",
    "    \"concepts\": [\n",
    "      \"Treatment group\",\n",
    "      \"Control group\"\n",
    "    ],\n",
    "    \"explanation\": \"False. The treatment group receives the intervention or new condition. The control group supplies the baseline comparison. Both groups contribute outcomes to the analysis.\",\n",
    "    \"retry_hint\": \"Compare the roles of the intervention group and the baseline comparison group.\",\n",
    "    \"id\": \"q3\",\n",
    "    \"cognitive_level\": \"recognition\",\n",
    "    \"reading\": \"../1001-ab-testing.html\",\n",
    "    \"choices\": {\n",
    "      \"A\": \"True\",\n",
    "      \"B\": \"False\"\n",
    "    }\n",
    "  },\n",
    "  {\n",
    "    \"format\": \"multiple_choice\",\n",
    "    \"prompt\": \"For an email experiment, the company records whether each customer makes a purchase. The purchase result is the:\",\n",
    "    \"concepts\": [\n",
    "      \"Outcome\",\n",
    "      \"Treatment group\"\n",
    "    ],\n",
    "    \"explanation\": \"An outcome is the measured result used to compare conditions. Assignment determines the condition a customer receives; the outcome records what happened afterward.\",\n",
    "    \"retry_hint\": \"Separate how a group is formed from what is measured for its members.\",\n",
    "    \"id\": \"q4\",\n",
    "    \"cognitive_level\": \"recognition\",\n",
    "    \"reading\": \"../1001-ab-testing.html\",\n",
    "    \"choices\": {\n",
    "      \"A\": \"Random assignment\",\n",
    "      \"B\": \"Control group\",\n",
    "      \"C\": \"Null model\",\n",
    "      \"D\": \"Outcome\"\n",
    "    }\n",
    "  },\n",
    "  {\n",
    "    \"format\": \"multiple_choice\",\n",
    "    \"prompt\": \"Which term describes subtracting one group average from another to summarize their difference?\",\n",
    "    \"concepts\": [\n",
    "      \"Difference in means\",\n",
    "      \"Test statistic\"\n",
    "    ],\n",
    "    \"explanation\": \"A difference in means compares group averages. A difference in proportions compares fractions with a specified outcome. Either can serve as a test statistic when it matches the measurement.\",\n",
    "    \"retry_hint\": \"Think about whether the summary compares averages, fractions, or counts.\",\n",
    "    \"id\": \"q5\",\n",
    "    \"cognitive_level\": \"recognition\",\n",
    "    \"reading\": \"../1001-ab-testing.html\",\n",
    "    \"choices\": {\n",
    "      \"A\": \"Difference in proportions\",\n",
    "      \"B\": \"Sample size\",\n",
    "      \"C\": \"Statistical power\",\n",
    "      \"D\": \"Difference in means\"\n",
    "    }\n",
    "  },\n",
    "  {\n",
    "    \"format\": \"multiple_choice\",\n",
    "    \"prompt\": \"Under a model where group labels have no effect on outcomes, an analyst repeatedly rearranges those labels. What is each rearrangement called?\",\n",
    "    \"concepts\": [\n",
    "      \"Permutation\",\n",
    "      \"Null model\"\n",
    "    ],\n",
    "    \"explanation\": \"A permutation rearranges labels on the observed outcomes to represent a null model in which those labels have no effect. It does not collect new observations from the population.\",\n",
    "    \"retry_hint\": \"Identify whether the analyst is rearranging existing labels or gathering new cases.\",\n",
    "    \"id\": \"q6\",\n",
    "    \"cognitive_level\": \"recognition\",\n",
    "    \"reading\": \"../1001-ab-testing.html\",\n",
    "    \"choices\": {\n",
    "      \"A\": \"Random sampling from a new population\",\n",
    "      \"B\": \"Permutation\",\n",
    "      \"C\": \"Blinding\",\n",
    "      \"D\": \"Effect size\"\n",
    "    }\n",
    "  },\n",
    "  {\n",
    "    \"format\": \"multiple_choice\",\n",
    "    \"prompt\": \"Two customer groups differ in both plan type and income, making it hard to isolate the plan effect. Which concept describes this mixing of effects?\",\n",
    "    \"concepts\": [\n",
    "      \"Confounding\",\n",
    "      \"Causality\"\n",
    "    ],\n",
    "    \"explanation\": \"Confounding occurs when effects are mixed so that a causal interpretation is difficult. An observed difference may reflect the plan, income, or both rather than a single isolated cause.\",\n",
    "    \"retry_hint\": \"Review the term for competing influences that are difficult to separate.\",\n",
    "    \"id\": \"q7\",\n",
    "    \"cognitive_level\": \"recognition\",\n",
    "    \"reading\": \"../1003-causality.html\",\n",
    "    \"choices\": {\n",
    "      \"A\": \"Confounding\",\n",
    "      \"B\": \"Blinding\",\n",
    "      \"C\": \"Statistical power\",\n",
    "      \"D\": \"Random assignment\"\n",
    "    }\n",
    "  },\n",
    "  {\n",
    "    \"format\": \"multiple_choice\",\n",
    "    \"prompt\": \"A team uses chance to select customers from its customer list, then uses chance again to allocate them to website versions. Which pairing describes the two steps?\",\n",
    "    \"concepts\": [\n",
    "      \"Random sampling\",\n",
    "      \"Random assignment\"\n",
    "    ],\n",
    "    \"explanation\": \"Random sampling selects customers from the population of interest. Random assignment allocates selected customers to experimental conditions. Recognizing both steps clarifies how selection differs from treatment allocation.\",\n",
    "    \"retry_hint\": \"Ask which step selects cases and which step allocates conditions.\",\n",
    "    \"id\": \"q8\",\n",
    "    \"cognitive_level\": \"connection\",\n",
    "    \"reading\": \"../1003-causality.html\",\n",
    "    \"choices\": {\n",
    "      \"A\": \"Random assignment, then random sampling\",\n",
    "      \"B\": \"Blinding, then random sampling\",\n",
    "      \"C\": \"Random sampling, then random assignment\",\n",
    "      \"D\": \"Permutation, then blinding\"\n",
    "    }\n",
    "  },\n",
    "  {\n",
    "    \"format\": \"true_false\",\n",
    "    \"prompt\": \"True or false: If customers choose their own service plans, a difference between the plans proves that the plan caused the difference.\",\n",
    "    \"concepts\": [\n",
    "      \"Confounding\",\n",
    "      \"Causality\"\n",
    "    ],\n",
    "    \"explanation\": \"False. Self-selected groups may differ in other relevant ways. Their association alone does not isolate a causal plan effect; confounding remains a possible explanation.\",\n",
    "    \"retry_hint\": \"Connect self-selection with the glossary cautions about causal interpretation.\",\n",
    "    \"id\": \"q9\",\n",
    "    \"cognitive_level\": \"connection\",\n",
    "    \"reading\": \"../1003-causality.html\",\n",
    "    \"choices\": {\n",
    "      \"A\": \"True\",\n",
    "      \"B\": \"False\"\n",
    "    }\n",
    "  },\n",
    "  {\n",
    "    \"format\": \"multiple_choice\",\n",
    "    \"prompt\": \"A manager asks how large the difference is in meaningful business units, rather than only how unusual it is under a null model. Which concept answers that question?\",\n",
    "    \"concepts\": [\n",
    "      \"Effect size\",\n",
    "      \"P-value\"\n",
    "    ],\n",
    "    \"explanation\": \"Effect size describes the magnitude of a difference in practical units. A p-value addresses evidence under a null model, while power concerns the chance of detecting a real effect.\",\n",
    "    \"retry_hint\": \"Separate the magnitude of a difference from evidence and detection probability.\",\n",
    "    \"id\": \"q10\",\n",
    "    \"cognitive_level\": \"connection\",\n",
    "    \"reading\": \"../1003-causality.html\",\n",
    "    \"choices\": {\n",
    "      \"A\": \"P-value\",\n",
    "      \"B\": \"Statistical power\",\n",
    "      \"C\": \"Effect size\",\n",
    "      \"D\": \"Sample size\"\n",
    "    }\n",
    "  }\n",
    "];\n",
    "\n",
    "  var legacyQuestions = [\n",
    "  {\n",
    "    \"id\": \"q1\",\n",
    "    \"prompt\": \"Which term matches this explanation? An analysis that compares outcomes from two groups.\",\n",
    "    \"choices\": {\n",
    "      \"A\": \"Two-sample comparison\",\n",
    "      \"B\": \"A/B test\",\n",
    "      \"C\": \"Treatment group\",\n",
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    "    },\n",
    "    \"format\": \"multiple_choice\",\n",
    "    \"cognitive_level\": \"recognition\",\n",
    "    \"concepts\": [\n",
    "      \"Two-sample comparison\"\n",
    "    ],\n",
    "    \"explanation\": \"Two-sample comparison: An analysis that compares outcomes from two groups. This is the glossary meaning used by this original question.\",\n",
    "    \"retry_hint\": \"Compare the related terms in the assigned chapter glossary; identify what the description refers to.\",\n",
    "    \"reading\": \"../1000-two-samples.html\"\n",
    "  },\n",
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    "    \"id\": \"q2\",\n",
    "    \"prompt\": \"Which term matches this explanation? The group receiving the intervention or new condition.\",\n",
    "    \"choices\": {\n",
    "      \"A\": \"Treatment group\",\n",
    "      \"B\": \"Control group\",\n",
    "      \"C\": \"Outcome\",\n",
    "      \"D\": \"Difference in means\"\n",
    "    },\n",
    "    \"format\": \"multiple_choice\",\n",
    "    \"cognitive_level\": \"recognition\",\n",
    "    \"concepts\": [\n",
    "      \"Treatment group\"\n",
    "    ],\n",
    "    \"explanation\": \"Treatment group: The group receiving the intervention or new condition. This is the glossary meaning used by this original question.\",\n",
    "    \"retry_hint\": \"Compare the related terms in the assigned chapter glossary; identify what the description refers to.\",\n",
    "    \"reading\": \"../1000-two-samples.html\"\n",
    "  },\n",
    "  {\n",
    "    \"id\": \"q3\",\n",
    "    \"prompt\": \"Which term matches this explanation? The measured result used to compare groups.\",\n",
    "    \"choices\": {\n",
    "      \"A\": \"Two-sample comparison\",\n",
    "      \"B\": \"Outcome\",\n",
    "      \"C\": \"A/B test\",\n",
    "      \"D\": \"Treatment group\"\n",
    "    },\n",
    "    \"format\": \"multiple_choice\",\n",
    "    \"cognitive_level\": \"recognition\",\n",
    "    \"concepts\": [\n",
    "      \"Outcome\"\n",
    "    ],\n",
    "    \"explanation\": \"Outcome: The measured result used to compare groups. This is the glossary meaning used by this original question.\",\n",
    "    \"retry_hint\": \"Compare the related terms in the assigned chapter glossary; identify what the description refers to.\",\n",
    "    \"reading\": \"../1000-two-samples.html\"\n",
    "  },\n",
    "  {\n",
    "    \"id\": \"q4\",\n",
    "    \"prompt\": \"Which term matches this explanation? Selecting observations from a population by chance.\",\n",
    "    \"choices\": {\n",
    "      \"A\": \"Two-sample comparison\",\n",
    "      \"B\": \"A/B test\",\n",
    "      \"C\": \"Treatment group\",\n",
    "      \"D\": \"Random sampling\"\n",
    "    },\n",
    "    \"format\": \"multiple_choice\",\n",
    "    \"cognitive_level\": \"recognition\",\n",
    "    \"concepts\": [\n",
    "      \"Random sampling\"\n",
    "    ],\n",
    "    \"explanation\": \"Random sampling: Selecting observations from a population by chance. This is the glossary meaning used by this original question.\",\n",
    "    \"retry_hint\": \"Compare the related terms in the assigned chapter glossary; identify what the description refers to.\",\n",
    "    \"reading\": \"../1000-two-samples.html\"\n",
    "  },\n",
    "  {\n",
    "    \"id\": \"q5\",\n",
    "    \"prompt\": \"Which term matches this explanation? A rearrangement used to simulate group labels under a null model.\",\n",
    "    \"choices\": {\n",
    "      \"A\": \"Treatment group\",\n",
    "      \"B\": \"Two-sample comparison\",\n",
    "      \"C\": \"A/B test\",\n",
    "      \"D\": \"Permutation\"\n",
    "    },\n",
    "    \"format\": \"multiple_choice\",\n",
    "    \"cognitive_level\": \"recognition\",\n",
    "    \"concepts\": [\n",
    "      \"Permutation\"\n",
    "    ],\n",
    "    \"explanation\": \"Permutation: A rearrangement used to simulate group labels under a null model. This is the glossary meaning used by this original question.\",\n",
    "    \"retry_hint\": \"Compare the related terms in the assigned chapter glossary; identify what the description refers to.\",\n",
    "    \"reading\": \"../1000-two-samples.html\"\n",
    "  },\n",
    "  {\n",
    "    \"id\": \"q6\",\n",
    "    \"prompt\": \"Which term matches this explanation? A summary used to measure the group difference.\",\n",
    "    \"choices\": {\n",
    "      \"A\": \"Two-sample comparison\",\n",
    "      \"B\": \"Test statistic\",\n",
    "      \"C\": \"A/B test\",\n",
    "      \"D\": \"Treatment group\"\n",
    "    },\n",
    "    \"format\": \"multiple_choice\",\n",
    "    \"cognitive_level\": \"recognition\",\n",
    "    \"concepts\": [\n",
    "      \"Test statistic\"\n",
    "    ],\n",
    "    \"explanation\": \"Test statistic: A summary used to measure the group difference. This is the glossary meaning used by this original question.\",\n",
    "    \"retry_hint\": \"Compare the related terms in the assigned chapter glossary; identify what the description refers to.\",\n",
    "    \"reading\": \"../1000-two-samples.html\"\n",
    "  },\n",
    "  {\n",
    "    \"id\": \"q7\",\n",
    "    \"prompt\": \"Which term matches this explanation? A claim that changing one factor changes an outcome.\",\n",
    "    \"choices\": {\n",
    "      \"A\": \"Causality\",\n",
    "      \"B\": \"A/B test\",\n",
    "      \"C\": \"Two-sample comparison\",\n",
    "      \"D\": \"Treatment group\"\n",
    "    },\n",
    "    \"format\": \"multiple_choice\",\n",
    "    \"cognitive_level\": \"recognition\",\n",
    "    \"concepts\": [\n",
    "      \"Causality\"\n",
    "    ],\n",
    "    \"explanation\": \"Causality: A claim that changing one factor changes an outcome. This is the glossary meaning used by this original question.\",\n",
    "    \"retry_hint\": \"Compare the related terms in the assigned chapter glossary; identify what the description refers to.\",\n",
    "    \"reading\": \"../1000-two-samples.html\"\n",
    "  },\n",
    "  {\n",
    "    \"id\": \"q8\",\n",
    "    \"prompt\": \"Which term matches this explanation? An inactive treatment used as a comparison.\",\n",
    "    \"choices\": {\n",
    "      \"A\": \"Two-sample comparison\",\n",
    "      \"B\": \"A/B test\",\n",
    "      \"C\": \"Placebo\",\n",
    "      \"D\": \"Treatment group\"\n",
    "    },\n",
    "    \"format\": \"multiple_choice\",\n",
    "    \"cognitive_level\": \"recognition\",\n",
    "    \"concepts\": [\n",
    "      \"Placebo\"\n",
    "    ],\n",
    "    \"explanation\": \"Placebo: An inactive treatment used as a comparison. This is the glossary meaning used by this original question.\",\n",
    "    \"retry_hint\": \"Compare the related terms in the assigned chapter glossary; identify what the description refers to.\",\n",
    "    \"reading\": \"../1000-two-samples.html\"\n",
    "  },\n",
    "  {\n",
    "    \"id\": \"q9\",\n",
    "    \"prompt\": \"Which term matches this explanation? The magnitude of a difference in practical units.\",\n",
    "    \"choices\": {\n",
    "      \"A\": \"Two-sample comparison\",\n",
    "      \"B\": \"Effect size\",\n",
    "      \"C\": \"A/B test\",\n",
    "      \"D\": \"Treatment group\"\n",
    "    },\n",
    "    \"format\": \"multiple_choice\",\n",
    "    \"cognitive_level\": \"recognition\",\n",
    "    \"concepts\": [\n",
    "      \"Effect size\"\n",
    "    ],\n",
    "    \"explanation\": \"Effect size: The magnitude of a difference in practical units. This is the glossary meaning used by this original question.\",\n",
    "    \"retry_hint\": \"Compare the related terms in the assigned chapter glossary; identify what the description refers to.\",\n",
    "    \"reading\": \"../1000-two-samples.html\"\n",
    "  },\n",
    "  {\n",
    "    \"id\": \"q10\",\n",
    "    \"prompt\": \"Which term matches this explanation? A structured test used to support a management decision.\",\n",
    "    \"choices\": {\n",
    "      \"A\": \"Two-sample comparison\",\n",
    "      \"B\": \"A/B test\",\n",
    "      \"C\": \"Business experiment\",\n",
    "      \"D\": \"Treatment group\"\n",
    "    },\n",
    "    \"format\": \"multiple_choice\",\n",
    "    \"cognitive_level\": \"recognition\",\n",
    "    \"concepts\": [\n",
    "      \"Business experiment\"\n",
    "    ],\n",
    "    \"explanation\": \"Business experiment: A structured test used to support a management decision. This is the glossary meaning used by this original question.\",\n",
    "    \"retry_hint\": \"Compare the related terms in the assigned chapter glossary; identify what the description refers to.\",\n",
    "    \"reading\": \"../1000-two-samples.html\"\n",
    "  }\n",
    "];\n",
    "  var legacyVersion = 'dsm-ch10-preview-before-2026-10-19';\n",
    "  var authoredQuestions = JSON.parse(JSON.stringify(questions));\n",
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    "      canvas_assignment_id: params.get('canvas_assignment_id') || params.get('assignment_id') || '',\n",
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    "      student_identifier: params.get('student_identifier') || params.get('student_id') || params.get('email') || ''\n",
    "    };\n",
    "  }\n",
    "\n",
    "  function loadSessionIdentity(identity, actions, submit, result) {\n",
    "    submit.disabled = true;\n",
    "    actions.classList.add('is-locked');\n",
    "    result.textContent = 'Sign in from the account menu to submit this assignment.';\n",
    "\n",
    "    return fetch('/api/v1/session.php', { credentials: 'same-origin' })\n",
    "      .then(function (response) { return response.ok ? response.json() : null; })\n",
    "      .then(function (payload) {\n",
    "        if (!payload || !payload.authenticated || !payload.identity) return identity;\n",
    "        identity.canvas_user_id = payload.identity.canvas_user_id || identity.canvas_user_id || '';\n",
    "        identity.student_identifier = payload.identity.student_identifier || identity.student_identifier || '';\n",
    "        submit.disabled = false;\n",
    "        actions.classList.remove('is-locked');\n",
    "        result.textContent = payload.identity.display_name ? 'Signed in as ' + payload.identity.display_name + '.' : 'Signed in.';\n",
    "        return identity;\n",
    "      })\n",
    "      .catch(function () { return identity; });\n",
    "  }\n",
    "\n",
    "  function renderQuestions(container) {\n",
    "    container.textContent = '';\n",
    "    questions.forEach(function (question, index) {\n",
    "      var card = document.createElement('div');\n",
    "      card.className = 'ch10-preview-question';\n",
    "      card.dataset.question = question.id;\n",
    "\n",
    "      var prompt = document.createElement('p');\n",
    "      prompt.appendChild(text((index + 1) + '. ' + question.prompt));\n",
    "      card.appendChild(prompt);\n",
    "\n",
    "      (attemptState ? attemptState.orders[question.id] : Object.keys(question.choices)).forEach(function (letter, position) {\n",
    "        var label = document.createElement('label');\n",
    "        var input = document.createElement('input');\n",
    "        input.type = 'radio';\n",
    "        input.name = question.id;\n",
    "        input.value = letter;\n",
    "        input.checked = !!(attemptState && attemptState.answers[question.id] === letter);\n",
    "        label.appendChild(input);\n",
    "        label.appendChild(text(String.fromCharCode(65 + position) + '. ' + question.choices[letter]));\n",
    "        card.appendChild(label);\n",
    "      });\n",
    "\n",
    "      var feedback = document.createElement('div');\n",
    "      feedback.className = 'ch10-preview-feedback';\n",
    "      feedback.setAttribute('aria-live', 'polite');\n",
    "      card.appendChild(feedback);\n",
    "      container.appendChild(card);\n",
    "    });\n",
    "  }\n",
    "\n",
    "  function collectAnswers(quiz) {\n",
    "    var answers = {};\n",
    "    questions.forEach(function (question) {\n",
    "      var selected = quiz.querySelector('input[name=' + question.id + ']:checked');\n",
    "      answers[question.id] = selected ? selected.value : '';\n",
    "    });\n",
    "    // Press stores this marker with the submitted answers; it is not a scored question.\n",
    "    answers.__question_set = attemptState ? attemptState.version : questionSetVersion;\n",
    "    if (attemptState) answers.preview_attempt = attemptState.token;\n",
    "    return answers;\n",
    "  }\n",
    "\n",
    "  function loadFeedbackPolicy() {\n",
    "    // Use the existing server release setting; a network failure must not unlock answers.\n",
    "    return fetch('/api/v1/assignment-settings.php?assignment_id=' + encodeURIComponent(quizId), {\n",
    "      credentials: 'same-origin'\n",
    "    })\n",
    "      .then(function (response) { return response.ok ? response.json() : null; })\n",
    "      .then(function (payload) {\n",
    "        answersUnlocked = !!(payload && payload.ok && payload.answers_unlocked === true);\n",
    "      })\n",
    "      .catch(function () { answersUnlocked = false; });\n",
    "  }\n",
    "\n",
    "  function applyFeedback(quiz, feedback) {\n",
    "    questions.forEach(function (question) {\n",
    "      var card = quiz.querySelector('[data-question=' + question.id + ']');\n",
    "      var message = card.querySelector('.ch10-preview-feedback');\n",
    "      var item = feedback[question.id];\n",
    "      message.className = 'ch10-preview-feedback';\n",
    "      var status = (!item || !item.submitted) ? 'No answer submitted.' :\n",
    "        (item.correct ? 'Correct.' : 'Review and try again.');\n",
    "      var guidance = answersUnlocked ? question.explanation : question.retry_hint;\n",
    "      message.textContent = status + ' ' + guidance;\n",
    "      var reading = document.createElement('a');\n",
    "      reading.href = question.reading || \"../1000-two-samples.html\";\n",
    "      reading.appendChild(text('Review this concept'));\n",
    "      message.appendChild(text(' '));\n",
    "      message.appendChild(reading);\n",
    "      message.classList.add(item && item.correct ? 'correct' : 'incorrect');\n",
    "    });\n",
    "  }\n",
    "\n",
    "  function initLegacyPreviewQuiz() {\n",
    "    var quiz = document.getElementById('ch10-preview-quiz');\n",
    "    if (!quiz || quiz.dataset.ready === 'true') return;\n",
    "    quiz.dataset.ready = 'true';\n",
    "\n",
    "    var identity = getParams();\n",
    "    var questionsContainer = document.getElementById('ch10-preview-questions');\n",
    "    var result = document.getElementById('ch10-preview-result');\n",
    "    var submit = document.getElementById('ch10-preview-submit');\n",
    "    var actions = quiz.querySelector('.ch10-preview-actions');\n",
    "    var reset = document.getElementById('ch10-preview-reset');\n",
    "\n",
    "    renderQuestions(questionsContainer);\n",
    "    loadSessionIdentity(identity, actions, submit, result);\n",
    "\n",
    "    submit.addEventListener('click', function () {\n",
    "      var answers = collectAnswers(quiz);\n",
    "      submit.disabled = true;\n",
    "      result.textContent = 'Submitting...';\n",
    "\n",
    "      fetch('/api/v1/quiz-attempts.php', {\n",
    "        method: 'POST',\n",
    "        headers: { 'Content-Type': 'application/json' },\n",
    "        credentials: 'same-origin',\n",
    "        body: JSON.stringify({\n",
    "          quiz_id: quizId,\n",
    "          question_set_version: questionSetVersion,\n",
    "          answers: answers,\n",
    "          student_identifier: identity.student_identifier || identity.canvas_user_id || '',\n",
    "          canvas_course_id: identity.canvas_course_id,\n",
    "          canvas_assignment_id: identity.canvas_assignment_id,\n",
    "          canvas_user_id: identity.canvas_user_id\n",
    "        })\n",
    "      })\n",
    "        .then(function (response) {\n",
    "          return response.text().then(function (text) {\n",
    "            var payload = null;\n",
    "            try {\n",
    "              payload = text ? JSON.parse(text) : null;\n",
    "            } catch (error) {\n",
    "              throw new Error('Server returned a non-JSON response (HTTP ' + response.status + '): ' + text.slice(0, 160));\n",
    "            }\n",
    "            if (!payload) {\n",
    "              throw new Error('Server returned an empty response (HTTP ' + response.status + '). Check that PHP is enabled for /api/v1/quiz-attempts.php.');\n",
    "            }\n",
    "            if (!response.ok || !payload.ok) {\n",
    "              throw new Error(payload.message || payload.error || 'Submission failed.');\n",
    "            }\n",
    "            return payload;\n",
    "          });\n",
    "        })\n",
    "        .then(function (payload) {\n",
    "          var best = (payload.best_score === null || typeof payload.best_score === 'undefined') ? payload.score : payload.best_score;\n",
    "          var attempt = (payload.attempt_count === null || typeof payload.attempt_count === 'undefined') ? '' : ' Attempt ' + payload.attempt_count + '.';\n",
    "          return loadFeedbackPolicy().then(function () {\n",
    "            applyFeedback(quiz, payload.feedback || {});\n",
    "            result.textContent = 'Submission saved.' + attempt + ' Score: ' + payload.score + ' / ' + payload.max_score + '. Best score: ' + best + ' / ' + payload.max_score + '. Canvas sync: ' + payload.canvas_sync_status + '.';\n",
    "            if (!answersUnlocked) result.textContent += ' Full explanations are available when answers are released.';\n",
    "          });\n",
    "        })\n",
    "        .catch(function (error) {\n",
    "          result.textContent = 'Could not save this attempt: ' + error.message;\n",
    "        })\n",
    "        .finally(function () {\n",
    "          submit.disabled = false;\n",
    "        });\n",
    "    });\n",
    "\n",
    "    reset.addEventListener('click', function () {\n",
    "      quiz.querySelectorAll('input[type=radio]').forEach(function (input) {\n",
    "        input.checked = false;\n",
    "      });\n",
    "      quiz.querySelectorAll('.ch10-preview-feedback').forEach(function (feedback) {\n",
    "        feedback.className = 'ch10-preview-feedback';\n",
    "        feedback.textContent = '';\n",
    "      });\n",
    "      result.textContent = '';\n",
    "    });\n",
    "  }\n",
    "\n",
    "\n",
    "  function initPreviewQuiz() {\n",
    "    // The legacy PHP host retains its existing fixed-order delivery until it migrates to Press.\n",
    "    if (!/(^|\\.)thinkpress\\.org$/.test(window.location.hostname) &&\n",
    "        !['localhost', '127.0.0.1'].includes(window.location.hostname)) return initLegacyPreviewQuiz();\n",
    "    var quiz = document.getElementById('ch10-preview-quiz');\n",
    "    if (!quiz || quiz.dataset.ready === 'true') return;\n",
    "    quiz.dataset.ready = 'true';\n",
    "\n",
    "    var identity = getParams();\n",
    "    var questionsContainer = document.getElementById('ch10-preview-questions');\n",
    "    var result = document.getElementById('ch10-preview-result');\n",
    "    var submit = document.getElementById('ch10-preview-submit');\n",
    "    var actions = quiz.querySelector('.ch10-preview-actions');\n",
    "    var reset = document.getElementById('ch10-preview-reset');\n",
    "\n",
    "    // Press owns this quiz's draft and option order; the generic runner must not restore older inputs over it.\n",
    "    quiz.classList.add('press-preview-managed');\n",
    "    var next = document.createElement('button');\n",
    "    next.type = 'button';\n",
    "    next.textContent = 'Start a new attempt';\n",
    "    next.hidden = true;\n",
    "    actions.appendChild(next);\n",
    "\n",
    "    function lockQuestions(locked) {\n",
    "      quiz.querySelectorAll('input[type=radio]').forEach(function (input) { input.disabled = locked; });\n",
    "      reset.disabled = locked;\n",
    "    }\n",
    "    function showState(payload) {\n",
    "      questions = attemptState.questions;\n",
    "      renderQuestions(questionsContainer);\n",
    "      lockQuestions(payload.completed);\n",
    "      submit.disabled = payload.completed;\n",
    "      next.hidden = !payload.completed;\n",
    "      if (!payload.completed) result.textContent = '';\n",
    "      if (attemptState.preserved_draft && !payload.completed) {\n",
    "        result.textContent = 'Resumed your saved answers with their original option order.';\n",
    "      }\n",
    "      if (payload.result) {\n",
    "        return loadFeedbackPolicy().then(function () {\n",
    "          applyFeedback(quiz, payload.result.feedback || {});\n",
    "          result.textContent = 'Saved attempt. Score: ' + payload.result.score + ' / ' + payload.result.max_score +\n",
    "            '. Best score: ' + payload.result.best_score + ' / ' + payload.result.max_score + '.';\n",
    "          if (!answersUnlocked) result.textContent += ' Full explanations are available when answers are released.';\n",
    "        });\n",
    "      }\n",
    "      return Promise.resolve();\n",
    "    }\n",
    "    renderQuestions(questionsContainer);\n",
    "    lockQuestions(true);\n",
    "    loadSessionIdentity(identity, actions, submit, result).then(function () {\n",
    "      if (submit.disabled) return;\n",
    "      submit.disabled = true;\n",
    "      result.textContent = 'Resuming your Preview...';\n",
    "      return stateRequest('resume').then(showState).catch(function (error) {\n",
    "        submit.disabled = true;\n",
    "        result.textContent = 'Could not resume this Preview: ' + error.message + ' Reload to retry.';\n",
    "      });\n",
    "    });\n",
    "\n",
    "    quiz.addEventListener('change', function (event) {\n",
    "      if (!event.target || event.target.type !== 'radio' || !attemptState) return;\n",
    "      saveAnswers(quiz).catch(function (error) { result.textContent = 'Answers not saved: ' + error.message; });\n",
    "    });\n",
    "\n",
    "    submit.addEventListener('click', async function () {\n",
    "      submit.disabled = true;\n",
    "      lockQuestions(true);\n",
    "      result.textContent = 'Submitting...';\n",
    "      try {\n",
    "        await saveAnswers(quiz);\n",
    "        var response = await fetch('/api/v1/quiz-attempts.php', {\n",
    "          method: 'POST', headers: { 'Content-Type': 'application/json' }, credentials: 'same-origin',\n",
    "          body: JSON.stringify({ quiz_id: quizId, answers: collectAnswers(quiz),\n",
    "            question_set_version: attemptState.version,\n",
    "            student_identifier: identity.student_identifier || identity.canvas_user_id || '',\n",
    "            canvas_course_id: identity.canvas_course_id, canvas_assignment_id: identity.canvas_assignment_id,\n",
    "            canvas_user_id: identity.canvas_user_id })\n",
    "        });\n",
    "        var payload = await response.json();\n",
    "        if (!response.ok || !payload.ok) throw new Error(payload.message || payload.error || 'Submission failed.');\n",
    "        await loadFeedbackPolicy();\n",
    "        applyFeedback(quiz, payload.feedback || {});\n",
    "        result.textContent = 'Submission saved. Attempt ' + payload.attempt_count + '. Score: ' + payload.score +\n",
    "          ' / ' + payload.max_score + '. Best score: ' + payload.best_score + ' / ' + payload.max_score + '.';\n",
    "        if (!answersUnlocked) result.textContent += ' Full explanations are available when answers are released.';\n",
    "        next.hidden = false;\n",
    "      } catch (error) {\n",
    "        result.textContent = 'Could not save this attempt: ' + error.message;\n",
    "        submit.disabled = false;\n",
    "        lockQuestions(false);\n",
    "      }\n",
    "    });\n",
    "\n",
    "    reset.addEventListener('click', function () {\n",
    "      submit.disabled = true;\n",
    "      stateQueue = stateQueue.catch(function () {}).then(function () { return stateRequest('clear'); });\n",
    "      stateQueue.then(function (payload) { result.textContent = ''; return showState(payload); })\n",
    "        .catch(function (error) { result.textContent = error.message; submit.disabled = false; });\n",
    "    });\n",
    "    next.addEventListener('click', function () {\n",
    "      next.disabled = true;\n",
    "      stateRequest('next').then(function (payload) { result.textContent = ''; return showState(payload); })\n",
    "        .catch(function (error) { result.textContent = error.message; })\n",
    "        .finally(function () { next.disabled = false; });\n",
    "    });\n",
    "  }\n",
    "\n",
    "  if (document.readyState === 'loading') {\n",
    "    document.addEventListener('DOMContentLoaded', initPreviewQuiz);\n",
    "  } else {\n",
    "    initPreviewQuiz();\n",
    "  }\n",
    "})();\n",
    "</script>"
   ]
  }
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