Midterm Solutions (CF)
I. (75 points) Multiple choice questions.
Use the following to answer questions 1 and 2: In order to determine if smoking causes cancer, researchers drew a large sample from the US adult population. For each adult they recorded whether the person had smoked regularly at any period in their life and whether the person had cancer. They then compared the proportion of cancer cases in those who had smoked regularly at some time in their lives with the proportion of cases in those who had never smoked regularly at any point in their lives. The researchers found that there was a higher proportion of cancer cases among those who had smoked regularly than among those who had never smoked regularly.
1. What type of study is this?
A) A block design.
B) An experiment, but not a double-blind experiment.
C) A double-blind experiment.
D) An observational study.
2. The researchers further refined the study by matching smokers and non-smokers along 19 dimensions, including income, occupation and others. They still found smokers were much more likely to develop cancer than comparable (along those 19 dimensions) nonsmokers. Which of the following arguments you consider to be the most forceful in challenging the causal relationship between smoking and cancer development?
A) A random experiment is the only acceptable approach in establishing this causal
B) The claimed causal relationship is still in doubt as long as there is any uncontrolled
C) People with lower income may be more likely to smoke and also more likely to develop
cancer due to other lifestyles associated with low income.
D) This is a retrospective study instead of a perspective study.
3. Choose the value z of a standard normal variable Z that 30% of the observations fall above z.
B) About 2 standard deviations above the mean