// Numbas version: finer_feedback_settings
{"name": "Demo accept NA or any counter-example", "extensions": [], "custom_part_types": [], "resources": [], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "question_groups": [{"pickingStrategy": "all-ordered", "questions": [{"name": "Demo accept NA or any counter-example", "tags": ["counterexample", "demo"], "metadata": {"description": "<p>Marking algorithm that allows NA or any correct counterexample.</p>", "licence": "Creative Commons Attribution 4.0 International"}, "statement": "<p>This demo shows how you can make a gap asking for a counter-example: if the statement is actually true, then the counterexample gap takes NA. If the statement is false, the gap takes any valid counterexample.</p>\n<p>The gaps have pattern restrictions, and the second part has an altered marking algorithm. For allowing any correct counterexample (without the \"NA\" bit), search also for a question by Christian Lawson-Perfect on \"Accept any symmetric matrix\". That's where I learnt that part of it.</p>", "advice": "", "rulesets": {}, "extensions": [], "variables": {"v1": {"name": "v1", "group": "Ungrouped variables", "definition": "vector((repeat(random(1..5),2)))", "description": "", "templateType": "anything"}, "v2": {"name": "v2", "group": "Ungrouped variables", "definition": "vector((repeat(random(1..5),2)))", "description": "", "templateType": "anything"}, "w1": {"name": "w1", "group": "Ungrouped variables", "definition": "vector(sqrt(n),pi)", "description": "", "templateType": "anything"}, "n": {"name": "n", "group": "Ungrouped variables", "definition": "random(2..5 except 4)", "description": "", "templateType": "anything"}, "w2": {"name": "w2", "group": "Ungrouped variables", "definition": "vector(-w1[0]/b,pi)", "description": "", "templateType": "anything"}, "b": {"name": "b", "group": "Ungrouped variables", "definition": "random(2..3)", "description": "", "templateType": "anything"}, "mu1": {"name": "mu1", "group": "Ungrouped variables", "definition": "random(2..4)", "description": "", "templateType": "anything"}, "mu2": {"name": "mu2", "group": "Ungrouped variables", "definition": "b*mu1", "description": "", "templateType": "anything"}, "e1": {"name": "e1", "group": "Ungrouped variables", "definition": "\"\\\\begin\\{pmatrix\\}1\\\\\\\\0\\\\\\\\0\\\\\\\\0\\\\end\\{pmatrix\\}\"", "description": "<p>first standard basis vector</p>", "templateType": "anything"}, "e2": {"name": "e2", "group": "Ungrouped variables", "definition": "\"\\\\begin\\{pmatrix\\}0\\\\\\\\1\\\\\\\\0\\\\\\\\0\\\\end\\{pmatrix\\}\"", "description": "", "templateType": "anything"}, "e3": {"name": "e3", "group": "Ungrouped variables", "definition": "\"\\\\begin\\{pmatrix\\}0\\\\\\\\0\\\\\\\\1\\\\\\\\0\\\\end\\{pmatrix\\}\"", "description": "", "templateType": "anything"}, "e4": {"name": "e4", "group": "Ungrouped variables", "definition": "\"\\\\begin\\{pmatrix\\}0\\\\\\\\0\\\\\\\\0\\\\\\\\1\\\\end\\{pmatrix\\}\"", "description": "", "templateType": "anything"}}, "variablesTest": {"condition": "v1<>v2", "maxRuns": 100}, "ungrouped_variables": ["v1", "v2", "w1", "w2", "n", "b", "mu1", "mu2", "e1", "e2", "e3", "e4"], "variable_groups": [], "functions": {}, "preamble": {"js": "", "css": ""}, "parts": [{"type": "gapfill", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "<p>[Here question about a true statement about vectors in \\(\\mathbb{R}^4\\).]</p>\n<p style=\"text-align: left;\">If you decided that the statement is false give a counterexample here. Write it into the gap as <code>vector(1,2,3,4)</code> with the numbers substituted by your chosen entries.&nbsp;(The marking algorithm will not understand fractions.) If you decided the statement is true (so there is no counterexample), then write <code>NA</code> into the gap.</p>\n<p style=\"text-align: center;\">Counterexample: [[0]]</p>\n<p></p>", "gaps": [{"type": "jme", "useCustomName": false, "customName": "", "marks": "1", "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "answer": "NA", "showPreview": true, "checkingType": "absdiff", "checkingAccuracy": 0.001, "failureRate": 1, "vsetRangePoints": 5, "vsetRange": [0, 1], "checkVariableNames": false, "singleLetterVariables": false, "allowUnknownFunctions": true, "implicitFunctionComposition": false, "mustmatchpattern": {"pattern": "vector($n,$n,$n,$n)`|NA", "partialCredit": 0, "message": "You should input a vector with four entries, or <code>NA</code>.", "nameToCompare": ""}, "valuegenerators": [{"name": "na", "value": ""}]}], "sortAnswers": false}, {"type": "gapfill", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "<p>[Here question about a false statement about vectors in \\(\\mathbb{R}^4\\).]</p>\n<p style=\"text-align: left;\">If you decided that the statement is false, give a counterexample here. Write it into the gap as <code>vector(1,2,3,4)</code> with the numbers substituted by your chosen entries. (The marking algorithm will not understand fractions.) If you decided that the statement is true (so no counterexample exists), then write <code>NA</code> into the gap. (Correct is any vector with non-zero fourth entry.)</p>\n<p style=\"text-align: center;\">Counter-example: [[0]]</p>", "gaps": [{"type": "jme", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "is_NA (Is the student's entry NA?):\n  matches(studentExpr,\"NA\")\n\nis_vector (Is the student's entry a vector with four entries?):\n  matches(studentExpr,\"vector(`+- $n,`+- $n,`+- $n,`+- $n)\")\n\nstudentVector (Make the student Entries into a vector):\n  if(is_vector,eval(studentExpr),false)\n\nhas_non_zero_fourth_entry (Does the student's answer have non-zero fourth entry?):\n  correctif(is_vector and studentVector[3]<>0)\n\nmark:\n    apply(studentExpr);\n    apply(forbiddenStringsPenalty);\n    apply(requiredStringsPenalty);\n    apply(failMatchPattern);\n    if(is_NA,\n      incorrect(\"Your answer is incorrect.\"); end(),\n      apply(has_non_zero_fourth_entry))", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "answer": "vector(0,0,0,1)", "showPreview": true, "checkingType": "absdiff", "checkingAccuracy": 0.001, "failureRate": 1, "vsetRangePoints": 5, "vsetRange": [0, 1], "checkVariableNames": false, "singleLetterVariables": false, "allowUnknownFunctions": true, "implicitFunctionComposition": false, "mustmatchpattern": {"pattern": "vector($n,$n,$n,$n)`|NA", "partialCredit": 0, "message": "You should input a vector with four entries, or <code>NA</code>.", "nameToCompare": ""}, "valuegenerators": []}], "sortAnswers": false}], "partsMode": "all", "maxMarks": 0, "objectives": [], "penalties": [], "objectiveVisibility": "always", "penaltyVisibility": "always", "type": "question", "contributors": [{"name": "Julia Goedecke", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/5121/"}]}]}], "contributors": [{"name": "Julia Goedecke", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/5121/"}]}