two catalysts may be used in a batch chemical process. twelve batches were prepared using catalyst 1, resulting in an average yield of 86 and a sample standard deviation of 3. fifteen batches were prepared using catalyst 2, and they resulted in an average yield of 89 with a stan- dard deviation of 2. assume that yield measurements are approximately normally distributed with the same standard deviation. (a) is there evidence at 1% significance level to support a claim that catalyst 2 produces a higher mean yield than catalyst 1? (b) find a 95% confidence interval on the difference in mean yields.