In this Excel Application, we will be calculating the 95% confidence interval for the SLEEP variable. To do this, we need to find the mean, x̄, and then find the maximum margin of error, E. Then, we can use the calculator to find the interval, (x̄ - E, x̄ + E).

• First, find the mean. Under the SLEEP column values, in cell F37, type =AVERAGE(F2:F36).

• Now, calculate the standard deviation in cell F38, by typing =STDEV(F2:F36).

• Now, we can find the maximum margin of error, E, that we need for the confidence interval.

To find the maximum margin of error, in cell F39, type = CONFIDENCE.T(0.05,F38,35).

(Note: the 0.05 is based on the 95% level of confidence, the F38 is the standard deviation, and the 35 is the size of our sample).