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Answer:
See below for answers and explanations
Step-by-step explanation:
<u>Part A</u>
Assuming that conditions have been met for the interval, we use the formula where
represents the sample mean,
represents the critical value,
represents the sample standard deviation, and
is the sample size.
The critical value of for an 80% confidence level with degrees of freedom
is equivalent to
Thus, we can compute the confidence interval:
Therefore, we are 80% confident that the true mean age of all customers is between 30.17 and 35.11 years.
<u>Part B</u>
The margin of error is