A large public utility company wants to compare the consumption of electricity during the summer season for single-family houses in two counties that it services. For each household sampled, the monthly electric bill is recorded with the following results:
(Note the italicized X below should have a line above it.)
X $115 $98
S $30 $18
n 25 21
(a) Is there evidence that the mean monthly bill is higher in County I than in County II?
(b) Estimate the mean difference between the monthly bill of County I and County II.
The solution contains hypothesis testing examples.