Use the Following Data for the Next Questions

Use the following data for the next questions. Biologists, researching the effects
of adding limestone sand as buffer for acid rain effects in streams, monitored the
pH levels of two streams each month for 36 months. The first stream had a mean
pH level of 6.8 with a standard deviation of 2.3. The control stream had a mean pH
level of 9.2 with a standard deviation of 1.5. Assume a .05 significance level for
testing the claim that the mean pH of the first stream was less (more acidic) than
the mean pH of the control stream. Also, assume the two samples are independent
simple random samples selected from normally distributed populations.
-Construct a 90% confidence interval for the difference between the two means.