# Statistics STA 2014 Week 10 homework

Objective:Use confidence intervals appropriately.

Section 9.1

22. You Explain It! Superstition: A USA Today/Gallup poll asked 1,006 adult Americans how much it would bother them to stay in a room on the 13th ?oor of a hotel. Interestingly, 13% said it would bother them. The margin of error was 3 percentage points with 95% con?dence. Which of the following represents a reasonable interpretation of the survey results? For those not reasonable, explain the ?aw.

(a) We are 95% con?dent that the proportion of adult Americans who would be bothered to stay in a room on the 13th ?oor is between 0.10 and 0.16.

(b) We are between 92% and 98% con?dent that 13% of adult Americans would be bothered to stay in a room on the 13th ?oor.

(c) In 95% of samples of adult Americans, the proportion who would be bothered to stay in a room on the 13th ?oor is between 0.10 and 0.16.

(d) We are 95% con?dent that 13% of adult Americans would be bothered to stay in a room on the 13th ?oor.

Section 9.2

8. (a) Find the t-value such that the area in the right tail is 0.02 with 19 degrees of freedom.

(b) Find the t-value such that the area in the right tail is 0.10 with 32 degrees of freedom.

(c) Find the t-value such that the area left of the t-value is 0.05 with 6 degrees of freedom. [Hint: Use symmetry.]