1. The credit manager of a large department store claims that the mean balance for the store's charge account customers is R3,280. An independent auditor selects a random sample of 18 accounts and finds a mean balance of R4,090.64 and a standard deviation of R1,470. If the manager's claim is not supported by these data, the auditor intends to examine all charge account balances. If the population of account balances is assumed to be approximately normally distributed, what action should the auditor take? (Remember to use the 4-step process.)

2. A law enforcement agent believes that at least 88% of the drivers stopped on Saturday nights for speeding are under the influence of alcohol. A sample of 66 drivers who were stopped for speeding on a Saturday night was taken. Eighty percent of the drivers in the sample were under the influence of alcohol. a) State the null and alternative hypothesis. b) What test statistics would you use to test the hypothesis above? c) Find the appropriate critical value. Two decimals. d) Calculate the test statistic and interpret your findings. (4)