Crawford Industries Purchases Step-Down Electrical Converters from Two Suppliers

Multiple Choice

Crawford Industries purchases step-down electrical converters from two suppliers.The converters from the two suppliers appear to have the same average life (measured in hours) but the variability in useful life appears be different for the units provided by the two suppliers.In random samples of 8 converters from supplier A and 8 converters from supplier B, the standard deviation in sample A was 40 hours; the standard deviation in sample B was 55 hours.Assume that converter life is normally distributed in each population.Test the null hypothesis that the population variance B is no greater than the population variancedeviation A, against the alternative hypothesis that the population variance B is greater than population variance A.Use a significance level of 5% for this one-tailed test and report the critical F (F_c) for the test.

A) 3.160
B) 6.013
C) 3.787
D) 2.965