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Columbia STAT UN1001 - Measurements, Mistakes, and Misunderstandings

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Copyright ©2005 Brooks/Cole, a division of Thomson Learning, Inc.Measurements,Mistakes, andMisunderstandingsChapter 3Copyright ©2005 Brooks/Cole, a division of Thomson Learning, Inc.2Thought Question 1:Want to find out what people felt to be themost important problem facing society today.Better to give a fixed set of choicesfrom which they must choose or anopen-ended question that allowed themto specify whatever they wished?What would be the advantages anddisadvantages of each approach?Copyright ©2005 Brooks/Cole, a division of Thomson Learning, Inc.3Thought Question 2:You and a friend are each doing a surveyto see if there is a relationship between heightand happiness.Without discussing in advance, you both attemptto measure the height and happiness of the same100 people.More likely to agree on measurement of heightor on measurement of happiness?Explain, discussing how you would measureeach characteristic.Copyright ©2005 Brooks/Cole, a division of Thomson Learning, Inc.4Thought Question 3:Newsletter distributed by politician to hisconstituents gave results of nationwide surveyon Americans’ attitudes about educational issues.One question: “Should your legislature adopt apolicy to assist children in failing schools to optout of that school and attend an alternativeschool—public, private, or parochial—of theparents’ choosing?”From wording of question, can you speculateon what answer was desired? Explain.Copyright ©2005 Brooks/Cole, a division of Thomson Learning, Inc.5Thought Question 4:At a swimming pool with a friend andbecome curious about the width of the pool.Friend has 12-inch ruler, with which he setsabout measuring the width. He reports thatthe width is 15.771 feet. (.771 ft = 9 ¼ inches)Do you believe the pool is exactly thatwidth? What is the problem?Copyright ©2005 Brooks/Cole, a division of Thomson Learning, Inc.6Thought Question 5:If you were to have your intelligence,or IQ, measured twice using astandard IQ test, do you think it wouldbe exactly the same both times?What factors might account for anychanges?Copyright ©2005 Brooks/Cole, a division of Thomson Learning, Inc.73.1 Simple MeasuresDon’t Exist• Important to understand how theinformation was collected andwhat was measured or asked.• Many measurements are complexand difficult.Copyright ©2005 Brooks/Cole, a division of Thomson Learning, Inc.83.2 It’s All in the Wording• About how fast were the cars going when theycontacted each other?Average response = 31.8 mph• About how fast were the cars going when theycollided with each other?Average response = 40.8 mphSimple changes of words can lead to big changes in answers.Example 1: How Fast Were They Going?Students asked questions after shown film of car accident.Copyright ©2005 Brooks/Cole, a division of Thomson Learning, Inc.92003 Survey of Teens and Drug UseTwo versions of same question.Half teens were asked about ‘buying’ these itemsand the other half about ‘obtaining’ them.Example 2: Is Marijuana Easy to BuyBut Hard to Get?Source: Original Source 13 on CD• Which is easiest for someone your age to buy:cigarettes, beer or marijuana?• Which is easiest for someone your age to obtain:cigarettes, beer or marijuana?Copyright ©2005 Brooks/Cole, a division of Thomson Learning, Inc.10Example 2: Is Marijuana Easy to BuyBut Hard to Get?Results:Note:Beer is easier to ‘obtain’ than marijuana,but marijuana is easier to ‘buy’ than beer.10%9%Don’t know/no response5%4%The Same19%34%Marijuana27%18%Beer39%35%Cigarettes“obtain” version“buy” versionResponseCopyright ©2005 Brooks/Cole, a division of Thomson Learning, Inc.11How much TV do you watch each day?A:B: 30 60 90 120 150 minutes 2.5 3.0 3.5 4.0 4.5 hoursA: 16.2% > 150 minutes B: 34.1% > 2.5 hoursCopyright ©2005 Brooks/Cole, a division of Thomson Learning, Inc.12Pitfalls when asking questions …1. Deliberate bias2. Unintentional bias3. Desire to please4. Asking the uninformed5. Unnecessary complexity6. Ordering of questions7. Confidentiality and anonymityCopyright ©2005 Brooks/Cole, a division of Thomson Learning, Inc.13Deliberate BiasQuestions can be deliberatelyworded to support a certain cause.Example:• Anti-abortion group’s question: “Do you agree thatabortion, the murder of innocent beings, should beoutlawed?”• Pro-choice group’s question: “Do you agree thatthere are circumstances under which abortion shouldbe legal, to protect the rights of the mother?Appropriate wording should not indicate a desired answer.Copyright ©2005 Brooks/Cole, a division of Thomson Learning, Inc.14Unintentional BiasQuestions are worded such that themeaning is misinterpreted by many.Example:• Do you use drugs? --- need to specify if you meanprescription drugs, illegal drugs, etc.• What is the most important date in your life? ---need to specify if you mean calendar date or socialengagement.The same word can have multiple meanings.Copyright ©2005 Brooks/Cole, a division of Thomson Learning, Inc.15Desire to PleaseMost respondents have a desire to pleasethe person who is asking the question.People tend to understate responses aboutundesirable social habits, and vice versa.Example:Estimate of prevalence of cigarette smokingbased on surveys do not match those basedon cigarette sales.Copyright ©2005 Brooks/Cole, a division of Thomson Learning, Inc.16Asking the UninformedPeople do not like to admit theydon’t know what you are talking about.Example:“When the American Jewish Committee studiedAmericans’ attitudes toward various ethnic groups,almost 30% of the respondents had an opinion aboutthe fictional Wisians, rating them in social standingabove a half-dozen other real groups, includingMexicans, Vietnamese and African blacks.”Source: Crossen (1994, p. 24)Copyright ©2005 Brooks/Cole, a division of Thomson Learning, Inc.17Unnecessary ComplexityIf questions are to be understood,they must be kept simple.Examples:• Too confusing: “Shouldn’t former drug dealersnot be allowed to work in hospitals after they arereleased from prison?”• Asking more than one question at once:“Do you support the president’s health care planbecause it would ensure that all Americans receivehealth coverage?”Copyright ©2005 Brooks/Cole, a division of Thomson Learning, Inc.18Ordering of QuestionsThe order in which questions


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