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Stat 100 Feb 8

Stat 100 Feb 8. Read Chapter 12, try 1-9. Ch. 12 Thought Question 1. Students in a class were asked whether they preferred an in-class or a take-home final Of 25 “A” (on midterm) students, 10 preferred take-home Of 50 “non-A” students (on midterm), 30 preferred take-home

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Stat 100 Feb 8

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  1. Stat 100 Feb 8 Read Chapter 12, try 1-9

  2. Ch. 12 Thought Question 1 • Students in a class were asked whether they preferred an in-class or a take-home final • Of 25 “A” (on midterm) students, 10 preferred take-home • Of 50 “non-A” students (on midterm), 30 preferred take-home • How would you display the data in a table?

  3. Contingency Table

  4. Marijuana Legalization and Gender • In the 1993 General Social Survey, a question was- • Do you think the use of marijuana should be made legal or not?

  5. Research Question • Is there a relationship between gender and opinion about legalization?

  6. Two-way Table of Counts

  7. Percents for each gender

  8. Appears to be Relationship • Percent favoring legalization differs for males and females • Is observed result “statistically significant?” • Statistically significant = we believe observed relationship holds in population. • We’ll study “significance” next time.

  9. Ch. 12 Thought Question 2 • Suppose a news article claimed that drinking coffee doubled your risk of developing a certain disease. • Assume this well-conducted research. • What additional information would you want before deciding whether or not to quit drinking coffee?

  10. What you should want to know • What is the actual risk of the disease (with or without coffee drinking) • How much coffee drinking? For how long? • Is there confounding? Other ways coffee drinkers may differ from non-coffee drinkers?

  11. Book Thought Question 4 • A recent study estimated that the "relative risk" of developing lung cancer if a woman smoked was 27.9. • What do you think is meant by the term relative risk?

  12. Comparing Risks • Relative Risk= Divide risk in one group by risk in other • It gives a multiplicative factor • Interpretation: Smokers’ risk = 27.9 times the risk for non-smokers

  13. Example • Of 92 8th grade students classified as “short,” 42 say they’ve been bullied • Of 111 8th grade students of normal height, 31 say they’ve been bullied. • What is the relative risk of being bullied for short students?

  14. Calculations • Risk for “short” = 42/92 = 0.456, or 45.6% • Risk for normal = 31/111 = 0.279, or 27.9% • Relative risk = 45.6 / 27.9 = 1.63 • Interpretation: Short students are 1.63 times as likely to have been bullied as students with normal height.

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