Factor 2x2c2 + 3xc2 − 35c2
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Answer:
The 98% confidence interval for the average credit card balance is
(564.04, 635.96).
Step-by-step explanation:
We have to calculate the 98% confidence interval on the average credit card balance.
The sample will consist of the n=30 customers that have credit card.
The sample has a mean of $600 and a standard deviation of $80.
As the population standard deviation is estimated from the sample standard deviation, we will use a t statistic.
The degrees of freedom are:
The critical value for a 98% CI and 29 degrees of freedom is t=2.463 (this can be looked up in a t-table).
Then, the margin of error is:
Then, the upper and lower bounds of the confidence interval are: