1)The delivery times for all food orders at a fast-food restaurant during the lunch hour are

normally distributed with a mean of 7.7 minutes and a standard deviation of 2.1 minutes.

Find the probability that the mean delivery time for a random sample of 16 such orders at

this restaurant is

a. between 7 and 8 minutes

b. within 2 minute of the population mean

2)The amounts of electricity bills for all households in a city have a skewed probability

distribution with a mean of $140 and a standard deviation of $30.

a. Comment on shape of the sampling distribution if a random sample of 85 households is

selected from this city.

b. Find the probability that the mean amount of electric bills for a random sample of 85

households selected from this city will be

i) between $132 and $136

ii) within $8 of the population mean

3)A random sample of 45 acres gave a mean yield of wheat equal to 41.2 bushels per acre

and standard deviation of 3 bushels,. Assuming that shape population distribution is

rightward. Construct a 99% confidence interval for the population mean. Draw graph