1. concentrations of a pollutant were measured at 25 locations in a lake after rains caused heavy runoff from surrounding areas. after a period of dry weather, they were measured again at the same locations. the data are in the file runoff. find a 90% confidence interval for the effect of runoff on pollutant concentrations.

2. repeat problem 1 treating the rainy and dry measurements as independent samples. compare the results. which is the better procedure?

An engineer is going to redesign an ejection seat for an airplane. the seat was designed for pilots weighing between 120 lb and 161 lb. the new population of pilots has normally distributed weights with a mean of 125 lb and a standard deviation of 28.1 lb. a)if a pilot is randomly selected, find the probability that his weight is between 120 lb and 161 lb.the probability is approximately? b. if 36 different pilots are randomly selected, find the probability that their mean weight is between 120 lb and 161 lb. the probability is approximately? c. when redesigning the ejection seat, which probability is more relevant? . part (b) because the seat performance for a single pilot is more important. b. part (b) because the seat performance for a sample of pilots is more important. c. part (a) because the seat performance for a sample of pilots is more important. d. part (a) because the seat performance for a single pilot is more important.