Professor Preston et al. (1978) studied the effectiveness of bank premiums (stoneware, calculators) given as an inducement to open bank accounts. They randomly selected a sample of 200 accounts each for “premium offered” and “no premium offered.” They found that 79 % of the accounts opened when a premium was offered and 89 % of accounts opened when a premium was not offered were retained over a 6-month period. Use these data to test whether P_x = 79 % is statistically different from P_y = 89 %. Do a 5 % test.