standard deviation and coefficient of varriation

Question

A sample of 18 employees at a company is monitored to see how long they break for lunch on a particular day. The following data is the lunch break (in minutes) for each worker: ,25 ,25 ,32 ,45 ,22 ,34 ,56 ,51 ,35 ,30 ,33 ,38 ,44 ,31 ,48 ,36 ,26 ,36 ; Question The standard deviation (in minutes) for this data is: (a) 91.60 (b) 10.07 (c) 9.57 (d) 9.54 (e) 9.27

Answer 1

First, you will want to calculate the mean, $E(X)$, by adding together the values and dividing by 18.

The next step is to find the variance. For this you will want to calculate $E(X^2)$, which can be found by summing the squares of each value and dividing by 18. In other words: $E(X^2)=(25^2+25^2+32^2+45^2+...)/18$

$Var=E(X^2)-E(X)^2$ and standard deviation is the square root of the variance.