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# Point Estimate and Confidence Interval

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The management of a department store is interested in estimating the difference between the mean credit purchases of customers using the store's credit card versus those customers using a national major credit card. You are given the following information.
Store's Card Major Credit Card
Sample size 64 49
Sample mean \$140 \$125
Population standard deviation \$10 \$8

a)A point estimate for the difference between the mean purchases of the users of the two credit cards is

b) At 95% confidence, the margin of error is

c) A 95% confidence interval estimate for the difference between the average purchases of the customers using the two different credit cards is

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#### Solution Preview

Please see attached file:
Confidence interval for difference between means (large sample size)
The management of a department store is interested in estimating the difference between the mean credit purchases of customers using the store's credit card versus those customers using a national major credit card. You are given the following information.
Store's Card Major Credit Card
Sample size 64 49
Sample mean \$140 \$125
Population standard deviation \$10 \$8

Data

Sample 1: Store's Card
Mean of sample 1= M1 = \$140
Standard deviation of sample 1= s1 = \$10 ...

#### Solution Summary

Calculates the point estimate and confidence interval for the difference between the mean purchases of the users of the two credit cards.

\$2.49