1. In order to investigate the effectiveness of a new cholesterol lowering drug, two separate studies were conducted. In the first study, 100 adults with high cholesterol were used, 50 of these adults were randomly assigned to the treatment group (those receiving the drug), and 50 of these adults were randomly assigned to the control group (those receiving a placebo, or harmless sugar pill). The mean cholesterol level in the treatment group was then compared to the control group.

In the second study, 100 adults with high cholesterol were given the drug. After an appropriate amount of time for the drug's effects to wear off, the 100 adults were then given the placebo. The mean difference in cholesterol readings for each individual was then analyzed.

In both studies, the adults (and the pill providers) did not know which of the pills they were taking.

• In the first study, what type of sampling method is being used?
• In the second study, what type of sampling method is being used?

2. Tom Lawrence investigated the profiles of the top executives in the U.S. banking industry. He sampled 16 executives and recorded the number of years of service at the same bank, which is assumed to have a normal distribution. He found that the sample had a sample mean of 23.43 and a standard deviation of 10.82. Construct a 95% confidence interval?