Question

Listed below are speeds (in mi/h) of cars on the New Jersey Turnpike by race of the driver. All cars are going in the same direction, and all of the cars are from New Jersey. The data are from Statlib and the authors are Joseph Kadane and John Lamberth. Find standard deviation. 74 77 69 71 77 69 72 75 74 72 Os=2.906 A O 8.44 OS--2.906 Os=2.096

Answer 1

The speeds of cars are 74, 77, 69, 71, 77, 69, 72, 75, 74, 72.

Let these numbers be denoted by x_i ; i = 1, 2, .......,10.

The sample size is n = 10.

r
= $\sum_{i=1}^{10}$ x_i / n

   = (74 + 77 + 69 + 71 + 77 + 69 + 72 + 75 + 74 + 72) / 10

   = 73

$\sum_{i=1}^{10}$x_i² = 74² + 77² + 69² + 71² + 77² + 69² + 72² + 75² + 74² + 72²

               = 53366

s² = ($\sum_{i=1}^{10}$x_i² - n * ²) / (n - 1)

r

    = (53366 - 10 * 73²) / 9

s² = 8.44

$\therefore$ s = $\sqrt{8.44}$

       = 2.906

Therefore, the standard deviation is 2.906