9.81 Window sizes in integrated circuit chips must be of fairly uniform size in order for the circuits to function properly. Thus, the variance of the window width measurements is an important quantity. Refer to the data of Exercise 9.79.

a Estimate the true variance of the post-etch window widths in a 95% confidence interval.

b Estimate the ratio of the variance of post-etch window widths to that of pre-etch window widths in a 95% confidence interval.

c What assumptions are necessary for your answers in parts

(a) and

(b) to be valid?