A random sample of 16 sheering pins is taken in a study of t

A random sample of 16 sheering pins is taken in a study of the Rockwell hardness of the head on the pin. Measurements on the Rockwell hardness were made for each of the 16 pins, yielding an average value of 62.2 with a sample standard deviation of 2.4. Assuming the measurements to be normally distributed, Construct a 95% C.I for the mean Rockwell hardness Construct a 95% C.l for the standard deviation of the Rockwell hardness.

Solution

n =16

Sample average = 62.2

sample s= 2.4

Normally distributed.

Margin of error = 1.96(std error) =