Question 10.217

10. Trying to quit smoking? Butt-Enders, a cigarette dependence reduction program, claims to lower the average number of cigarettes smoked for its participants. A sample of 10 participants smoked the following numbers of cigarettes on a randomly chosen day before and after attending Butt-Enders. Assume that the differences are normally distributed.

Participant 1 2 3 4 5
Before 40 20 60 30 50
After 20 0 40 30 20
Participant 6 7 8 9 10
Before 60 20 40 30 20
After 60 20 20 0 20
  1. Find a 90% confidence interval for the population mean difference in number of cigarettes smoked.
  2. Use your confidence interval to test, at level of significance , whether the population mean difference in number of cigarettes smoked differs from 0.