Question

A highway speed monitor is located on the side of the road that has a speed limit of 45 mph. The system records the speeds of passing vehicles. The data below shows the speeds of the first 9 cars that pass.

46 56 45 44 45 61 55 53 39

What is the standard deviation, to the nearest tenth, based on the posted speed limit, 45 mph?

Answer 1

You add 46+56+45+44+45+61+55+53+39 and you get 49.3333 rounded to the nearest tenth the standard deviation would be 49mph

Answer 2

First you need to find the mean on these numbers that is step one in finding standard deviation. so this is 44.2. now you need to subtract the mean from each number and square the result. after that step you now have these numbers.... 3.24, 139.24, .64, .4,.64,282.24,116.64,77.44,27.04. now the next step is to find the mean of these numbers. you get 71.9 appx.. now all you do is square root this number you get 8.5 when you round to the nearest thenth