Construct confidence interval

1. Construct a 90% confidence interval for the population mean of the weights of elephants.

The standard deviation of the weights of elephants is known to be approximately 16 pounds.

We wish to construct a 90% confidence interval for the mean weight of newborn elephant

calves. Seventy newborn elephants are weighed. The sample mean is 250 pounds. The sample standard deviation is 12 pounds. Round your answer to two decimal places.

Define the random variable X in words.

4. The mean age for all Foothill College students for a recent Fall term was 33.2. The

population standard deviation has been pretty consistent at 15. Suppose that twenty-five

Winter students were randomly selected. The mean age for the sample was 30.4. We are

interested in the true mean age for Winter Foothill College students.