Question

a.) A contractor wishes to lower heating bills by using a special type of insulation in houses. The mean of the heating bill announced by the Energy Resource is 85. To determine if the special insulation will reduce heating costs, the contractor collects 20 heating bills from houses that already use the special type of insulation. The average of a heating bill for these 20 houses is 78. State the null and alternative hypotheses.

b.) Treadlife of 2 brands of tires were compared by installing one of each kind on the rear of 3 different cars. After 3 weeks of driving on the tires, measurements were taken on the tread thickness (in cm) for each tire, resulting in the following table:

Car	Brand A	Brand B
1	1.2	1.3
2	1.4	1.5
3	1.1	1.5

On the basis of an appropriate normal model assumption, a 95% confidence interval for the difference in mean tread thickness (Brand B-Brand A) is?

c.) You are given the following hypotheses:
H 0 : μ = 30
H a : μ > 30
We know that the sample standard deviation is 9 and the sample size is 81. For what sample mean would the p-value be equal to 0.10?  

Answer 1