Question

An automobile shop manager timed 27 employees and recorded the time, in minutes, it took them to change a water pump. Assuming normality, use Excel to find the 99% confidence interval for the true mean. Round your answers to three decimal places and use increasing order.
18.4 16.1 19.5 16.5 12.5 17.2 13.8 17.9 19.1 9.8 23.8 18.7 19.1 15.0 19.2 17.0 11.5 15.7 22.5 23.7 19.9 17.6 15.0 17.8 20.7 14.2 15.4

Answer 1

Answer:

Excel attached with the solution.

Step-by-step explanation:

Mean

$\bar{x}=\frac{\sum x_{i}}{n}$

Standard deviation

$sd=\sqrt{\frac{\sum (x_{i}-\bar{x})}{n-1}}$

Confidence interval

$\bar{x} \pm z_{\alpha}*sd/\sqrt{n}$

The formulas used are in the Excel file attached.

Download xlsx