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In a batch chemical process, two catalysts are compared for their effect on the output of the process reaction. A sample of 12 batches was prepared using catalyst 1 and a sample of 10 batches was obtained using catalyst 2. The 12 batches for which catalyst 1 was used gave a sample mean yield of 85 with a sample standard deviation of 4, while the 10 batches for which
catalyst 2 was used gave a sample mean yield of 81 with a sample standard deviation of 5. Let Mi and M2 denote the true mean yields using catalysts 1 and 2, respectively. Compute the lower limit of a 90% confidence interval for H1 - H2, assuming that the data are normally distributed.