# A new purification unit is installed in a chemical process. Before and after installation data was collected

## Question:

Before (1): Sample mean = 9.85, Sample variance = 6.79, Number of samples = 10

After (2): Sample mean = 8.08, Sample variance = 6.18, Number of samples = 8

a. Can you conclude that the two variances are equal using a two-sided 95% confidence interval?

b. Can you conclude that the new purification device has reduced the mean percentage of impurity using a two-sided 95% confidence interval?

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**Related Book For**

## Managing Controlling and Improving Quality

**ISBN:** 978-0471697916

1st edition

**Authors:** Douglas C. Montgomery, Cheryl L. Jennings, Michele E. Pfund