measures of dispersion

Range: is the subtraction of the greatest value minus the lowest value.

Mean deviation: It is the mean of the deviations of the mean:

 

Variance: 

 

  Standard deviation:

Now we are going to see a video about how to use the calculator in Statisitics:

 

  Example: 20 families are asked about how many children they have:

xi	fi	deviation |xi-μ|
0	1	2,7
1	2	1,7
2	6	0,7
3	6	0,3
4	3	1,3
5	2	2,3
Σ	20

μ = 2,7       range = 5        MD = 1,03        σ = 1,27        VAR = 1,61