3. The manager of an appliance store, after noting that the average daily sales was only 12 units, decided to adopt a new marketing strategy. Daily sales under this strategy were recorded for 90 days after which period the average was found to be 15 units with a s.d. of 4 units. Does this indicate that the new marketing strategy increased the daily sales? Assume that the distribution of daily sales are approximately normally distributed. Use a = .01. Given: ,1 = 12 units n = 90 days 3? = 15 units 3 = 4 units a: = 0.01