1.The Dean of the Business School wants to estimate the mean number of hours worked per week by students. A sample of only 12 students showed a mean of 24 hours with a standard deviation of 4 hours. Find the 95 percent confidence interval for the population mean.Round final answers to two decimal places.

lower limit hours...................

upper limit hours.............

2.A consumer group would like to estimate the mean monthly electricity charge for a single family house in July (within $4) using a 90 percent level of confidence. Based on similar studies the standard deviation is estimated to be $20.00. How large a sample is required?

3.The mean weight of trucks traveling on a particular section of Highway 401 is not known. A provincial highway inspector needs an estimate of the mean. He selects a random sample of 49 trucks passing the weighing station and finds the mean is 15.8 tons, with a standard deviation of the sample of 3.8 tons. What is the 95 percent interval for the population mean?Round final answers to one decimal place.

Lower Limit,..............tons

Upper Limit.........................tons