Last year the records of Dairy Land Inc., a convenience store chain, showed the mean amount spent by a customer was $30. A sample of 40 transactions this month revealed the mean amount spent was $33. Assume that the population standard deviation, s, is known and equal to $12.
a. At the 0.05 significance level, can we conclude that the mean amount spent has increased?
b. What is the p-value? Follow the five-step hypothesis testing procedure.