posted by betsy on .
A study of peach trees found that the average number of peaches per tree was 625. The standard deviation of the population is 140 peaches per tree. Ascientist wishes to find 80% confidence interval for the mean number of peaches per tree. How many trees does she need to sample to obtain an average accurate to within 16 peaches per tree?
Jim Tree sells Christmas trees. The mean length of the trees purchased was 68 inches with a standard deviation of 10 inches. Jim wants to know what per cent of his sales were more than 84 inches tall. He can use the standard normal distribution to help him.