Question

5.15 An investigator polls common cold sufferers, asking them to estimate the number of hours of physical discomfort caused by their most recent colds. Assume that their estimates approximate a normal curve with a mean of 83 hours and a standard deviation of 20 hours.

1. What proportion suffered for between 1 and 3 days, that is, between 24 and 72 hours?

2. What proportion suffered for between 2 and 4 days?

3. Another survey found that people with colds who took daily doses of vita-min C suffered, on the average, for 61 hours. What proportion of the original survey (with a mean of 83 hours and a standard deviation of 20 hours) suffered for more than 61 hours?

4. What proportion of the original survey suffered for exactly 61 hours? (Be careful!)

Answer 1