Dave the jogger runs the same route every day (about 2.2 miles)

Dave the jogger runs the same route every day (about 2.2 miles). On 18 consecutive days, he recorded the number of steps using a pedometer. The results were

3,450	3,363	3,228	3,360	3,304	3,407	3,324	3,365	3,290
3,289	3,346	3,252	3,237	3,210	3,140	3,220	3,103	3,129

a) Construct a 95% confidence interval for the true mean number of steps Dave takes on his run. (Round your answers to 4 decimal places.)

b) What sample size would be needed to obtain an error of ± 20 steps with 95% confidence? (Enter your answer as a whole number (no decimals). Use a z-value taken to three decimal places in your calculations.)

SHOW THE WORK IF POSSIBLE. I know the mean is 3278.7222 and the standard deviation is 97.0535.

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