Thought question 1. Thought question 2

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Phyllis Craig
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1 Thought question 1 Advice columnists sometimes ask readers to write and express their feelings about certain topics. Ann Landers asked whether they thought engineers make good husbands. Do you think the responses she got are representative of public opinion? Thought question 2 Taste tests of new products are often done by having people taste both the new product and an old familiar standard. Do you think the results would be biased if the person handing the products to the respondents knew which was which?

2 Thought question 3 Nicotine patches are attached to the arm of someone who is trying to quit smoking and dispense nicotine into the blood. Suppose you read a study showing nicotine patches were twice as effective in getting people to quit smoking as control patches (made to look like the real thing). Further, suppose you are a smoker trying to quit. What questions would you want answered about how the study was done and its results before you decided whether to try the patches?

3 What Are Data? Data = plural word referring to a collection of numbers or other pieces of information to which meaning has been attached. Numbers 1, 3, and 10 are not necessarily data, but become data when told these were weight gains in grams of 3 infants in Salks heartbeat study. Don t trust headlines! Newspapers rarely present actual data. Meaning attached to data and results depends on how well info was obtained and summarized.

4 Critical components to a good sample 1. The source of the research and of the funding 2. The researchers who had contact with the participants 3. The individuals or objects studied and how they were selected 4. The exact nature of the measurements made or questions asked 5. The setting in which the measurements were taken 6. Differences in the groups being compared, in addition to the factor of interest 7. The extent or size of any claimed effects or differences

5 1. The source of the research and of the funding Three key drivers for studies Governments and private companies need to have data in order to make wise policy decisions Researchers at universities are paid to ask and answer interesting questions about the world around us Companies want to convince consumers that their products work better 2. The researchers who had contact with the participants How would you be biased if a person in full running gear asked you how often you exercise? How would you be biased if a person dressed in full police uniform asked you about illegal drugs? Double-blind is sometimes necessary

6 3. The individuals or objects studied and how they were selected Until recently, only men would be asked to test new drugs Often participation is rewarded with a small fee Voluntary survey participation attracts passionate believers 4. The exact nature of the measurements made or the questions asked How do you define eg exercise or breakfast? Would the term street people rather that homeless people elicit different reactions? Exact and consistent wording should be used (and known).

7 5. The setting in which the measurements were taken The time of day a survey is conducted may exclude certain groups The time of year may influence the results Phone/mail/online surveys are more anonymous 6. Differences in the groups being compared, in addition to the factor of interest What other factors may have influenced the comparison (we call these confounding factors). Key in the difference between observational studies and randomized experiments. Confounding factors in observational studies may shows spurious causations Randomized experiments control for confounding factors

8 7. The extent of size of any claimed effects or differences A drug may be an improvement, but how much of an improvement? In aspirin study, aspirin may reduce the risk from 17 heart attacks in 1000 to 9.4 in 1000.

9 Hypothetical example

10 Hypothetical example

11 Mediterranean diet and heart disease jul7_10.html Case study 2.2: Brooks shoes

12 Thought question 1 Want to find out what people felt to be the most important problem facing society today. Better to give a fixed set of choices from which they must choose or an open-ended question that allowed them to specify whatever they wished? What would be the advantages and disadvantages of each approach? Thought question 2 Newsletter distributed by politician to his constituents gave results of nationwide survey on Americans attitudes about educational issues. One question: Should your legislature adopt a policy to assist children in failing schools to opt out of that school and attend an alternative school public, private, or parochial of the parents choosing? From wording of question, can you speculate on what answer was desired? Explain.

13 Thought question 3 If you were to have your intelligence, or IQ, measured twice using a standard IQ test, do you think it would be exactly the same both times? What factors might account for any changes? Thought question 4 At a swimming pool with a friend and become curious about the width of the pool. Friend has 12-inch ruler, with which he sets about measuring the width. He reports that the width is feet. (.771 ft = 9.25 inches) Do you believe the pool is exactly that width? What is the problem?

14 Simple measures don t exist! Examples Beer is easier to obtain than marijuana, but marijuana is easier to buy than beer. Cars went faster before they collided than before they contacted.

15 The 7 pitfalls of a questionnaire Deliberate bias Unintentional bias Desire to please Asking the uninformed Unnecessary complexity Ordering of questions Confidentiality and anonymity

16 Deliberate bias Questions can be deliberately worded to support a certain cause. Anti-abortion groups question: Do you agree that abortion, the murder of innocent beings, should be outlawed? Pro-choice groups question: Do you agree that there are circumstances under which abortion should be legal, to protect the rights of the mother? Unintentional bias Questions are worded such that the meaning is misinterpreted by many. Do you use drugs? What is the most important date in your life?

17 Desire to please Most respondents have a desire to please the person who is asking the question. Estimate of prevalence of cigarette smoking based on surveys do not match those based on cigarette sales. Asking the uninformed People do not like to admit they dont know what you are talking about. When the American Jewish Committee studied Americans attitudes toward various ethnic groups, almost 30% of the respondents had an opinion about the fictional Wisians. [Source: Crossen (1994, p. 24)]

18 Unnecessary complexity If questions are to be understood, they must be kept simple. Too confusing: Shouldnt former drug dealers not be allowed to work in hospitals after they are released from prison? Asking more than one question at once: Do you support the presidents health care plan because it would ensure that all Americans receive health coverage? Ordering of questions The order in which questions are presented can change the results. To what extent do you think teenagers today worry about peer pressure related to drinking alcohol? Name the top five pressures you think face teenagers today.

19 Confidentiality and anonymity People answer differently based on degree to which they are anonymous. Confidentiality: researcher promises not to release identifying information about respondents. Anonymity: researcher doesnt know identity of respondents.

Lecture 1. Benefits of Using Statistics

Lecture 1. Benefits of Using Statistics Lecture 1 Benefits of Using Statistics Thought Question 1: A recent newspaper article concluded that smoking marijuana at least three times a week resulted in lower grades in college. How do you think