Esp To help determine the most effective way for us to advertise our new supermarket, we've hired a consulting firm to investigate coupon use when coupons are mailed directly to individuals' homes. The consulting firm has produced the following histogram, which summarizes the coupon use information (the daily percentage of customers who use at least one coupon in a purchase) for each of the past 64 days. Frequency ? 30- 28 25- 20- OO 16 15 10 Ed D 5 7 9 11 13 Percentage of customers Based on this histogram, estimate the standard deviation of the sample of 64 percentages. M Carry your intermediate computations to at least four decimal places, and round your answer to at least one decimal place. (If necessary, consult a list of formulas.)