Crawford Industries purchases step-down electrical converters from two suppliers. The converters from the two suppliers appear...

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 two suppliers. In random samples of 9 converters from supplier A and 9 converters from supplier B, the variance in the sample A was 600; the variance in the sample B was 2800. Assume that the life of the converters is normally distributed in each population. Test the hypothesis that the variances of the two populations are equal, using a significance level of 2%. Report the F statistic (F_stat) for the test.

a) 3.160

b) 6.178

c) 4.667

d) 2.965

Solutions

Expert Solution

F statistic (F_stat) for the test is 4.667 (Option C is correct. Calculation is shown below)

Following are steps for performing F-test for the Equality of Two Population Variances:

Let s₁² = Variance of Sample B, s₂² = Variance of Sample A

Ho: σ₁² = σ₂²

Ha: σ₁² ≠ σ₂²

Here, σ₁² = Population Variance of Sample B, σ₂² = Population Variance of Sample A

Thus, there is not enough evidence to claim that the variability in useful life is different for the two suppliers.

orchestra answered 1 year ago

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