Use R to for this exercise. [In your R document, type comments (lines that start with #) to both (i) explain what your R commands do, and (ii) answer questions in the problem below.] A researcher intends to estimate the effect of a drug on the scores of human subjects performing a task of psychomotor coordination. The members of a random sample of 12 subjects were given the drug prior to testing. The mean score in this group was 11.06, and the sample variance was 11.56. An independent random sample of 8 subjects was used as a control group and given a placebo prior to testing. The mean score in this control group was 13.67, and the sample variance was 14.75. Assuming that the population distributions are normal with equal variances, find a 90% confidence interval for the difference between the population mean scores.

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