Question

Ten bearings made by a certain process have a mean diameter of 0.905 cm with a standard deviation of 0.0050 cm. Assuming that the data may be viewed as a random sample from a normal population, construct a 95% confidence interval for the actual average diameter of bearings made by this process and interpret.

Answer 1

At 95% confidence interval the critical value is t^* = 2.262

The 95% confidence interval for population mean is

+/- t^* * s/

= 0.905 +/- 2.262 * 0.005/

= 0.905 +/- 0.004

= 0.901, 0.909

We are 95% confident that true population mean diameter lies between the confidence bounds 0.901 and 0.909.