Question

According to industry specifications, the standard deviation of gasket thicknesses for a given application must be no more than 3 thousandths of an inch. In a random sample of 25 gaskets produced by one of the firms, the sample standard deviation is found to be 3.7 thousandths of an inch. Assuming the population of thicknesses is normally distributed, and using alpha equal 0.025, examine whether the firm could be in violation of the industry specification

Answer 1

H0: <= 3

Ha: > 3

Test statistics

= ( n - 1) S2 / 2

= ( 25 - 1) * 3.72 / 32

= 36.51

Chi-square critical value at 0.025 level with 24 df = 39.364

SInce test statistics < 39.364, fail to reject H0

We do not have sufficient evidence to support the claim that the firm could be in violation

of the industry specification.