Two catalysts in a batch chemical process are being compared for their effect on the output of the process reaction. A sample of 15 batches was prepared using catalyst 1 and gave an average yield...

Two catalysts in a batch chemical process are being compared for their effect on the output of the process reaction. A sample of 15 batches was prepared using catalyst 1 and gave an average yield of 79 with a sample standard deviation of 4. A sample of 12 batches was prepared using catalyst 2 and gave an average yield of 73 and a sample standard deviation of 3.  Find a 90​% confidence interval for the difference between the population​ means, assuming that the populations are approximately normally distributed with equal variances.