Two catalysts may be used in a batch chemical process. twelve batches were prepared using catalyst 1, resulting in an average yield of 84 and a sample standard deviation of 3. fifteen batches were prepared using catalyst 2, and they resulted in an average yield of 92 with a standard deviation of 2. assume that yield measurements are approximately normally distributed with the same standard deviation. (a) is there evidence to support the claim that catalyst 2 produces higher mean yield than catalyst 1? use (b) find a 99% confidence interval on the difference in mean yields that can be used to test the claim in part (a). round your answer to two decimal places (e. g. 98.76).