A study was conducted to determine the effectiveness of a speed limit sign. The speeds of cars at the 65 mph sign were:
58, 60, 65, 65, 70, 70, 71, 74, 85, 88
The mean speed of cars at the 65 mph speed limit sign is calculated by adding up all the speeds and dividing by the total number of speeds:
58 + 60 + 65 + 65 + 70 + 70 + 71 + 74 + 85 + 88 = 676
676 / 10 = 67.6
Therefore, the mean speed of cars at the 65 mph speed limit sign is 67.6 mph.