Question

The accompanying data represent the running times of files produced by two motion-picture companies. Assume that the running-time differences are approximately normally distributed. Construct a 90% confidence interval for . If a 90% on confidence interval for u-u, were created, should it be assumed that 94 Company Time (minutes) 99 115 89 96 | 94 87 121 90 172 90 122 Click here to view page 1 of the table of critical values of the F-distribution, for alpha = 0.05. Click here to view page 2 of the table of critical values of the F-distribution, for alpha = 0.05. The confidence interval is (Round to three decimal places as needed.)

Answer 1

The statistical software output for this problem is:

Two sample variance confidence interval: 2 Variance of I 2 Variance of II 02 012/022 Ratio of two variances 90% confidence interval results: Num. DF Den. DF Sample Ratio L. Limit Ratio U. Limit 4 6 0.10262167 0.022635417 0.63247091 1

Hence,

90% confidence interval will be:

$\small \mathbf{0.023} \leq \frac{\sigma_1^2}{\sigma_2^2} \leq \mathbf{0.632}$