Data on the numbers of hospital admissions resulting from motor vehicle crashes are given below for Fridays on the 6th of a month and Fridays on the following 13th of the same month. Assume that the paired sample data is a simple random sample and that the differences have a distribution that is approximately normal. Construct a95% confidence interval estimate of the mean of the population of differences between hospital admissions. Use the confidence interval to test the claim that when the 13th day of a month falls on aFriday, the numbers of hospital admissions from motor vehicle crashes are not affected.

Friday the 6th

11

9

3

3

8

Fridaythe13th

15

14

14

12

13

In thisexample, d is the mean value of the differences d for the population of all pairs ofdata, where each individual difference d is defined as the number of hospital admissions on Friday the 6th minus the number of hospital admissions on Friday the 13th. Find the95% confidence interval.