Question

Journal for Engineering Industry carries a study of deep hole drilling under drill chip congestion. Test to determine whether the true standard deviation of drill chip lengths differs from 75 mm. The study considers a sample of 50 drill chips and sample standard deviation s = 50.2. Use a significance level of α = .05.

Answer 1

The null and alternate hypothesis are:

H0:

Ha:

The test statistic is given by:

Since this is a two-tailed test, so the critical-values are given by:

and

Since test statistic 21.7778 does not lie between the critical values, so it lies in the rejection region. So we have sufficient evidence to reject the null hypothesis H0.

Thus we can conclude .