Dispersion
Mean deviation about mean For ungrouped data: , where is the mean given by
Mean deviation about mean For grouped data: , where is the mean given by and
Example:
Calculate mean deviation about mean for the following data:
Class
0 – 10
10 – 20
20 – 30
30 – 40
Frequency
21
19
49
11
Solution:
Here, assumed mean (a) = 25 and class size (h) = 10
Class
Frequency (fi)
Mid-point (xi)
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