A manufacturing process yield steel ball bearings with a diameter that is normally distributed with a mean of 12.5mm and a standard deviation of 0.

A manufacturing process yield steel ball bearings with a diameter that is normally distributed with a mean of 12.5mm and a standard deviation of 0.18mm. You suspect that an improvement to the process will reduce the standard deviation a random sample of 20 bearings had a mean of 12.6 and standard deviation of 0.13. Test your claim of a lower standard deviation at a 5% significance level