Practice Problems



Practice Problems

Ex 1) One of your distributors reports an average of 150 sales per day for the distributorship. You suspect that this average is not accurate, so you randomly select 35 days and determine the number of sales each day. The sample mean is 143 daily sales with a standard deviation of 15 sales. At α= 0.01, is there enough evidence to doubt the distributor’s reported average?

Ex 2) The CEO of the firm claims that the mean work day of the firm’s accountants is less than 8.5 hours. A random sample of 35 of the firm’s accountants has a mean work day of 8.2 hours with a standard deviation of 0.5 hours. At α= 0.01, test the CEO’s claim.

Ex 3) An automotive battery manufacturer guarantees that the mean reserve capacity of a certain battery is greater than 1.5 hours. To test this claim, you randomly select a sample of 50 batteries and find the mean reserve capacity to be 1.55 hours with a standard deviation of 0.32 hour. At α= 0.10, so you have enough evidence to support the manufacturer’s claim?

Ex 4) A company that makes cola drinks states that the mean caffeine content per one 12-ounce bottle of cola is 40 milligrams. Suppose you work as a quality control manager and are asked to verify this claim. During your tests, you find that a random sample of thirty 12-ounce bottles of cola has a mean caffeine content of 39.2 milligrams with a standard deviation of 7.5 milligrams. At α= 0.01, can you reject the company’s claim?

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