Question: Twenty-five volunteers who had developed cold symptoms within the last 24 hours were given zinc lozenges to take every 2 to 3 hours until their cold symptoms were gone. The mean overall duration of symptoms was 4.5 days with a standard deviation of 1.6 days.

The selected cases have a distribution which appears to be symmetric and bell-shaped.

a. Construct a 99% confidence interval for the mean overall duration of symptoms in a

population of individuals who used zinc lozenges.

b. In a previous test, the mean overall duration of symptoms for volunteers who were

told to drink an herbal tea for relief of their symptoms was 7 days. Based on your

confidence interval, do you think that using the lozenges reduces the overall duration

of symptoms compared to using the herbal tea?