Description
Problem 1 (2 points)
In the United States in 2007, the proportion of adults age 21-24 who had no medical
insurance was 28.1%. A survey of 75 recent college graduates in this age range finds that
30 of them are without insurance. Does this support a difference from the nationwide?
• Perform a two-sided significance test for a proportion, following the procedure of
seven steps in the lecture note (choose a significance level of 0.05).
• Use the related function in R to report the p-value. What’s your conclusion based on
the result?
Problem 2 (4 points)
In the past 30 days, a cell-phone store has sold 150 Apple iPhone and had 14 returned. It
has sold 125 Samsung Galaxy and had 15 returned. Is there statistical evidence that Apple
has a smaller chance of being returned than Samsung?
• Perform a one-sided significance test for proportion difference, following the procedure of seven steps in the lecture note (choose a significance level of 0.05).
• Use the related function in R to report the p-value. What’s your conclusion based on
the result?
Problem 3 (4 points)
For the babies dataset in the package UsingR, the variable age contains the mother’s age
and the variable dage contains the father’s age.
• Perform a two-sided significance test of the null hypothesis of equal ages against
the alternative that the ages are different in the sampled population, following the
procedure of seven steps in the lecture note (choose a significance level of 0.05).
1
• Use the related function in R to report the p-value. What’s your conclusion based on
the result?
2
