21. Impurities A pharmaceutical manufacturer is concerned about the variability of the impurities from shipment to shipment from two different suppliers.

To compare the variation in percentage impurities, the manufacturer selects 10 shipments from each of the two suppliers and measures the percentage of impurities in the raw material for each shipment. The sample means and variances are shown in the table.

a. Do the data provide sufficient evidence to indicate a difference in the variability of the shipment impurity levels for the two suppliers? Test using a 5.01. Based on the results of your test, what recommendation would you make to the pharmaceutical manufacturer?

b. Find a 99% confidence interval for 2 2  and interpret your results.

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Supplier A Supplier B X =1.89 x=1.85 s = 273 $=.094 n =10 n-10