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The expected number is given by:
\n\\[\\simplify[]{{p0 / 100} * {n1} + {p1 / 100} * {n2} + {p2 / 100} * {n3} + {p3 / 100} * {n4} + {p4 / 100} * {n5} + {p5 / 100} * {n6} + {p6 / 100} * {n7} + {p7 / 100} * {n8} + {p8 / 100} * {n9} = {ecom}}\\]
\nWe want the probability that the number of {episodes} exceeds $\\var{ecom}$
\nThis is the probability that the number exceeds $\\var{rdexp}$ and is
\n\\[\\sum_{i=\\var{rdexp+1}}^{i=8}\\left( \\mbox{Probability complaints}=i\\right)=\\simplify[]{{strexceed} }= \\var{probexceed/100}\\]
", "rulesets": {"std": ["all", "fractionNumbers", "!collectNumbers", "!noLeadingMinus"]}, "parts": [{"prompt": "Find the expected number of {episodes} per {period}.
\nAnswer to $2$ decimal places
\nExpected number = [[0]]
", "marks": 0, "gaps": [{"allowFractions": false, "marks": 2, "maxValue": "{ecom+0.01}", "minValue": "{ecom-0.01}", "correctAnswerFraction": false, "showCorrectAnswer": true, "scripts": {}, "type": "numberentry", "showPrecisionHint": false}], "showCorrectAnswer": true, "scripts": {}, "type": "gapfill"}, {"prompt": "What is the probability that the number of {episodes} will exceed the expected number?
\nAnswer to $2$ decimal places.
\nProbability = [[0]]
", "marks": 0, "gaps": [{"allowFractions": false, "marks": 2, "maxValue": "{probexceed/100+0.01}", "minValue": "{probexceed/100-0.01}", "correctAnswerFraction": false, "showCorrectAnswer": true, "scripts": {}, "type": "numberentry", "showPrecisionHint": false}], "showCorrectAnswer": true, "scripts": {}, "type": "gapfill"}], "statement": "\nThe probabilities that {idef} {thing} will receive {episodes} per {period} about its {activity} are given by the following table:
\nComplaints | \n0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
---|---|---|---|---|---|---|---|---|---|
Probability | \n$\\var{p0/100}$ | \n$\\var{p1/100}$ | \n$\\var{p2/100}$ | \n$\\var{p3/100}$ | \n$\\var{p4/100}$ | \n$\\var{p5/100}$ | \n$\\var{p6/100}$ | \n$\\var{p7/100}$ | \n$\\var{p8/100}$ | \n
Answer the following two parts:
\n ", "type": "question", "variable_groups": [], "variablesTest": {"maxRuns": 100, "condition": ""}, "variables": {"strexceed": {"definition": "if(ecom>3,p4/100+'+'+p5/100+'+'+p6/100+'+'+p7/100+'+'+p8/100,if(ecom>4,p5/100+'+'+p6/100+'+'+p7/100+'+'+p8/100,if(ecom>5,p6/100+'+'+p7/100+'+'+p8/100,p3/100+'+'+p4/100+'+'+p5/100+'+'+p6/100+'+'+p7/100+'+'+p8/100)))", "templateType": "anything", "group": "Ungrouped variables", "name": "strexceed", "description": ""}, "idef": {"definition": "'an'", "templateType": "anything", "group": "Ungrouped variables", "name": "idef", "description": ""}, "period": {"definition": "'day'", "templateType": "anything", "group": "Ungrouped variables", "name": "period", "description": ""}, "episodes": {"definition": "'complaints'", "templateType": "anything", "group": "Ungrouped variables", "name": "episodes", "description": ""}, "rdexp": {"definition": "floor(ecom)", "templateType": "anything", "group": "Ungrouped variables", "name": "rdexp", "description": ""}, "probexceed": {"definition": "if(ecom>3,p4+p5+p6+p7+p8,if(ecom>4,p5+p6+p7+p8,if(ecom>5,p6+p7+p8,100-p0-p1-p2)))", "templateType": "anything", "group": "Ungrouped variables", "name": "probexceed", "description": ""}, "check": {"definition": "p0+p1+p2+p3+p4+p5+p6+p7+p8", "templateType": "anything", "group": "Ungrouped variables", "name": "check", "description": ""}, "thing": {"definition": "'airline'", "templateType": "anything", "group": "Ungrouped variables", "name": "thing", "description": ""}, "u1": {"definition": "round(d*random(70..100)/100)", "templateType": "anything", "group": "Ungrouped variables", "name": "u1", "description": ""}, "u3": {"definition": "u1", "templateType": "anything", "group": "Ungrouped variables", "name": "u3", "description": ""}, "u2": {"definition": "u1", "templateType": "anything", "group": "Ungrouped variables", "name": "u2", "description": ""}, "ecom": {"definition": "(n1*p0+n2*p1+n3*p2+n4*p3+n5*p4+n6*p5+n7*p6+n8*p7+n9*p8)/100", "templateType": "anything", "group": "Ungrouped variables", "name": "ecom", "description": ""}, "p7": {"definition": "p8+u1", "templateType": "anything", "group": "Ungrouped variables", "name": "p7", "description": ""}, "p2": {"definition": "p1+t2", "templateType": "anything", "group": "Ungrouped variables", "name": "p2", "description": ""}, "p3": {"definition": "r-p0-p1-p2", "templateType": "anything", "group": "Ungrouped variables", "name": "p3", "description": ""}, "p0": {"definition": "s", "templateType": "anything", "group": "Ungrouped variables", "name": "p0", "description": ""}, "p1": {"definition": "p0+t1", "templateType": "anything", "group": "Ungrouped variables", "name": "p1", "description": ""}, "p6": {"definition": "p7+u2", "templateType": "anything", "group": "Ungrouped variables", "name": "p6", "description": ""}, "d": {"definition": "round(t/15)", "templateType": "anything", "group": "Ungrouped variables", "name": "d", "description": ""}, "p4": {"definition": "t-p8-p7-p6-p5", "templateType": "anything", "group": "Ungrouped variables", "name": "p4", "description": ""}, "p5": {"definition": "p6+u3", "templateType": "anything", "group": "Ungrouped variables", "name": "p5", "description": ""}, "p8": {"definition": "d", "templateType": "anything", "group": "Ungrouped variables", "name": "p8", "description": ""}, "t2": {"definition": "t1", "templateType": "anything", "group": "Ungrouped variables", "name": "t2", "description": ""}, "t1": {"definition": "round(s*random(70..100)/100)", "templateType": "anything", "group": "Ungrouped variables", "name": "t1", "description": ""}, "n8": {"definition": "7", "templateType": "anything", "group": "Ungrouped variables", "name": "n8", "description": ""}, "n9": {"definition": "8", "templateType": "anything", "group": "Ungrouped variables", "name": "n9", "description": ""}, "s": {"definition": "round(r/10)", "templateType": "anything", "group": "Ungrouped variables", "name": "s", "description": ""}, "r": {"definition": "random(45..65)", "templateType": "anything", "group": "Ungrouped variables", "name": "r", "description": ""}, "t": {"definition": "100-r", "templateType": "anything", "group": "Ungrouped variables", "name": "t", "description": ""}, "activity": {"definition": "'luggage handling'", "templateType": "anything", "group": "Ungrouped variables", "name": "activity", "description": ""}, "n1": {"definition": "0", "templateType": "anything", "group": "Ungrouped variables", "name": "n1", "description": ""}, "n2": {"definition": "1", "templateType": "anything", "group": "Ungrouped variables", "name": "n2", "description": ""}, "n3": {"definition": "2", "templateType": "anything", "group": "Ungrouped variables", "name": "n3", "description": ""}, "n4": {"definition": "3", "templateType": "anything", "group": "Ungrouped variables", "name": "n4", "description": ""}, "n5": {"definition": "4", "templateType": "anything", "group": "Ungrouped variables", "name": "n5", "description": ""}, "n6": {"definition": "5", "templateType": "anything", "group": "Ungrouped variables", "name": "n6", "description": ""}, "n7": {"definition": "6", "templateType": "anything", "group": "Ungrouped variables", "name": "n7", "description": ""}}, "metadata": {"notes": "\n \t\t7/07/2012:
\n \t\tAdded tags.
\n \t\tChecked calculation.
\n \t\t22/07/2012:
\n \t\tAdded description.
\n \t\tTicked stats extension box.
\n \t\t31/07/2012:
\n \t\tAdded tags.
\n \t\tQuestion appears to be working correctly.
\n \t\t20/12/2012:
\n \t\tCould increase the number of scenarios by using random string variables. Query tag added for that.
\n \t\tAlso very cumbersome use of variables. But no change proposed for now.
\n \t\tChecked calculation, OK. Added tested1 tag.
\n \t\t21/12/2012:
\n \t\tAlthough asks for solution to 2 dps, there is no rounding as the raw values are to 2 dps. Added sc tag for possible scenarios.
\n \t\t", "description": "Given a probability mass function $P(X=i)$ with outcomes $i \\in \\{0,1,2,\\ldots 8\\}$, find the expectation $E$ and $P(X \\gt E)$.
", "licence": "Creative Commons Attribution 4.0 International"}, "showQuestionGroupNames": false, "question_groups": [{"name": "", "pickingStrategy": "all-ordered", "pickQuestions": 0, "questions": []}], "contributors": [{"name": "Bill Foster", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/6/"}]}]}], "contributors": [{"name": "Bill Foster", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/6/"}]}