The variance is the mean of the squares of the deviations from x bar.

Standard deviation- the amount the largest and smallest numbers are away from the mean which is the average.

You find this by adding up all numbers then dividing by the numbers given.

Statistic- a number that describes some characteristic of a set of data.

To find standard deviaton you must use the following formula: s = square root of sum Xi^2 / n - X^2.

N= number of numbers

Xi= given numbers

X=mean of numbers

Example 1:

find standard deviation of 3 4 5 6 7

Xi Xi^2

3 9

4 16

5 25

6 36

7 49

Now add all squared answers and get 135. Now plug into formula.

To find the mean 3+4+5+6+7/5 = 5

sqaure root of 135/5 - 5^2 = square root of 2 = 1.41