Exam 4: Categorical Data: Comparisons and Associations

Assume the estimated odds ratio of obesity for the amount of weekly exercise (in minutes) is 0.93 (95% CI: 0.88, 0.99). Interpret this odds ratio for every minute and for 30-minute increases in exercising time.

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Question 1

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For every minute increase in exercising time, the odds ratio of obesity is decreased by 7%.
To obtain the odds ratio for every 30 minutes, we need to find the beta estimate first. Since exp(b) =0.93, b = ln(0.93). exp(30*ln(0.93)) = 0.11. Thus, for every 30 minutes increase in exercising time, the odds of obesity is decreased by (1-0.11)*100% = 89%. Since the confidence interval does not contain 1, the true odds ratio is not 1.

In the following scenarios, p = the probability of lung cancer. If the odds ratio estimate is 1.2, interpret for the following variables: a.age (continuous) b.education level (graduate school vs. high school) c.race (Black vs. White) d.smoking status (smoker vs. nonsmoker)

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Question 2

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a.The odds ratio of lung cancer is increased by 20% for every unit of increase in age.
b.The odds of lung cancer for people with graduate school degree is 1.2 times that of people with high school degree.
c.The odds of lung cancer for Black is 1.2 times that of White.
d.The odds of lung cancer for smokers is 1.2 times that of nonsmokers.

Which of the following is NOT an advantage of a pie chart?

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Question 3

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Briefly describe the similarity and difference between odds and risks. At what value of odds and risks will the probability of success be larger than the probability of failure?

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Question 4

Choose the most appropriate graphical presentation (pie chart or bar graph) for the following examples. Provide a rationale for your choice. a.To show the composition of racial distribution of a certain disease. b.To compare the proportion of smoking between males and females. c.To show an association between weight perception and age groups. d.To compare the number of cases of flu in each month

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Question 5

Describe how confidence intervals are used to determine whether an odds ratio is different than 1?

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Question 6

Briefly explain how the expected and observed cell counts are obtained. How do they influence the significance of the hypothesis test?

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Question 7

Why is it inappropriate to estimate risks directly in a case-control (retrospective) study?

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Question 8

When is it appropriate to interpret odds ratio as relative risk?

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Question 9

Briefly describe the difference between a case-control study and a cohort study in terms of the way data are collected. What measure of association is appropriate in each study?

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Question 10

The chi-square test of independence is used to assess which of the following hypotheses?

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Question 11

Suppose an odds ratio between gender (male, female) and smoking status (yes, no) is 2.5. Explain why it is incorrect to interpret the odds ratio as "the probability of smoking for males is 2.5 times that for females." Provide a correct interpretation.

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Question 12

The confidence interval width decreases as which of the following increases?

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Question 13

Specify an appropriate test (nonzero correlation test, row mean scores differ test, and general association test) for the following types of categorical variables. Justify the choice. a.education level versus social class (upper, middle, lower) b.gender versus anxiety rating (none, moderate, severe) c.race versus political affiliation

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Question 14

What is the denominator(s) used to calculate the percentages of the first cell.

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Question 15

Can a variable be regarded as both ordinal and dichotomous? Why or why not?

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Question 16

Which of the following is NOT required to determine the sample size for a test of two proportions?

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Question 17

For the first cell in the following contingency table, interpret the frequency, percent, row percent, and column percent.

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Question 18

Identify the following variables as nominal, ordinal, or dichotomous. Provide a justification for your choice. a.Types of diabetes: type 1 (insulin-dependent), type 2 (non-insulin-dependent), gestational diabetes mellitus. b.Time to recurrence: 0-2 years, 2-4 years, more than 4 years. c.Clinic sites: Lexington, Covington, Frankfort, Nashville, Bowling Green. d.Smoking status: smoker, nonsmoker. e.Levels of body mass index (BMI): normal, overweight, obese. Types of vaccine administration: oral, injection, puncture. f.Types of residency: urban, rural.

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Question 19

Which of the following is NOT a good descriptive statistic for categorical variables?

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Question 20

Showing 1 - 20 of 20

Assume the estimated odds ratio of obesity for the amount of weekly exercise (in minutes) is 0.93 (95% CI: 0.88, 0.99). Interpret this odds ratio for every minute and for 30-minute increases in exercising time.

In the following scenarios, p = the probability of lung cancer. If the odds ratio estimate is 1.2, interpret for the following variables: a.age (continuous) b.education level (graduate school vs. high school) c.race (Black vs. White) d.smoking status (smoker vs. nonsmoker)

Which of the following is NOT an advantage of a pie chart?

Briefly describe the similarity and difference between odds and risks. At what value of odds and risks will the probability of success be larger than the probability of failure?

Describe how confidence intervals are used to determine whether an odds ratio is different than 1?

Briefly explain how the expected and observed cell counts are obtained. How do they influence the significance of the hypothesis test?

Why is it inappropriate to estimate risks directly in a case-control (retrospective) study?

When is it appropriate to interpret odds ratio as relative risk?

Briefly describe the difference between a case-control study and a cohort study in terms of the way data are collected. What measure of association is appropriate in each study?

The chi-square test of independence is used to assess which of the following hypotheses?

Suppose an odds ratio between gender (male, female) and smoking status (yes, no) is 2.5. Explain why it is incorrect to interpret the odds ratio as "the probability of smoking for males is 2.5 times that for females." Provide a correct interpretation.

The confidence interval width decreases as which of the following increases?

What is the denominator(s) used to calculate the percentages of the first cell.

Can a variable be regarded as both ordinal and dichotomous? Why or why not?

Which of the following is NOT required to determine the sample size for a test of two proportions?

For the first cell in the following contingency table, interpret the frequency, percent, row percent, and column percent.

Which of the following is NOT a good descriptive statistic for categorical variables?

An Overview of Statistical Concepts

Continuous Data- Making Comparisons

Continuous Data: Correlation and Regression

A Dichotomous Outcome: Confounding and Regression

Count Data

Time to Event Data

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