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Electricity consumption by single-family homes in two separate countries

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

Use a level of significance of 0.01 or (99% confidence), and use statistical inference (confidence intervals or tests of hypotheses).


(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.


Solution Summary

The solution contains hypothesis testing examples.