A business researcher wants to estimate the average number of years of experience an account manager has working with the company before getting promoted to account manager. Eight account managers are randomly selected and asked how long they worked with the company before becoming an account manager. The resulting answers were: 1.2, 4.0, 3.6, 0.7, 5.8, 3.3, 2.8, 4.1

Use Excel and these data to compute a 90% confidence interval to estimate the average length of time an account manager spent working for the company before they were promoted to account manager. Print out your answer.

Formula for confidence interval:

CI90 = mean ± 1.645(sd/√n)

You will have to determine the mean and standard deviation. Sample size = 8

Using the formula by hand will double check your calculations.

To compute a 90% confidence interval for the average length of time an account manager spent working for the company before being promoted, we can use the following steps in Excel:

Step 1: Enter the data into a column in Excel. Let's say you have entered the data into column A, starting from cell A1.

Step 2: Calculate the sample mean (x-bar) and the sample standard deviation (s) using the AVERAGE and STDEV functions in Excel. In cell B1, enter the formula "=AVERAGE(A1:A8)" to calculate the sample mean. In cell B2, enter the formula "=STDEV(A1:A8)" to calculate the sample standard deviation.

Step 3: Calculate the standard error (SE) using the formula: SE = s / √n, where s is the sample standard deviation and n is the sample size. In cell B3, enter the formula "=B2/SQRT(8)" to calculate the standard error.

Step 4: Calculate the margin of error (ME) using the formula: ME = t * SE, where t is the t-score associated with the desired confidence level and degrees of freedom. Since we have a sample size of 8, our degrees of freedom are 7. The t-score for a 90% confidence level and 7 degrees of freedom can be found using the T.INV function in Excel. In cell B4, enter the formula "=T.INV(1-0.1/2, 7)" to calculate the t-score. Then, in cell B5, enter the formula "=B4 * B3" to calculate the margin of error.

Step 5: Calculate the lower and upper bounds of the confidence interval. In cell B6, enter the formula "=B1 - B5" to calculate the lower bound. In cell B7, enter the formula "=B1 + B5" to calculate the upper bound.

Step 6: Format the cells B1, B5, B6, and B7 as number with desired decimal places.

The resulting 90% confidence interval for the average length of time an account manager spent working for the company before being promoted would be the values in cells B6 (lower bound) and B7 (upper bound).

Make sure to print out the values in B6 and B7 to obtain the answer.