Find the standard deviation of the Percent Change in percent change in market share for Average Market Share per the control cities. Month +9 2 +4 Test cities 3 "+10 4 +1 +9 2 - 9 Control cities 3 -7 0 The standard deviation of the percent change in market share for the control cities is (Simplify your answer. Type an integer or decimal rounded to the nearest hundredth as needed.)