A travel agent is interested in the average price of a hotel room during the summer in a resort community. The agent randomly selects 18 hotels from the community and determines the price of a regular room with a king size bed. The average price of the room for the sample was $150 with a standard deviation of $40. Assume the prices are normally distributed. Construct an interval to estimate the true average price of a regular room with a king size bed in the resort community with 99% confidence. Round the endpoints to two decimal places, if necessary.

The electric cooperative needs to know the mean household usage of electricity by its non-commercial customers in kWh per day. They would like the estimate to have a maximum error of 0.13 kWh. A previous study found that for an average family the standard deviation is 2.1 kWh and the mean is 15.8 kWh per day. If they are using a 99% level of confidence, how large of a sample is required to estimate the mean usage of electricity? Round your answer up to the next integer.

The thicknesses of 90 randomly selected aluminum sheets were found to have a standard deviation of 1.59. Construct the 98% confidence interval for the population standard deviation of the thicknesses of all aluminum sheets in this factory. Round your answers to two decimal places.

A toy manufacturer wants to know how many new toys children buy each year. A sample of 686 children was taken to study their purchasing habits. Construct the 85% confidence interval for the mean number of toys purchased each year if the sample mean was found to be 6.8. Assume that the population standard deviation is 2.1. Round your answers to one decimal place.