Question

Calculate the mean deviation from the mean for the scores given below:
$15,11,13,20,26,18,21$

Answer 1

Arrange the scores in an order:
$11,13,15,18,20,21,26$.
You know how to calculate the mean for the set of scores. Just take the sum of the scores and divide it by the number of scores to get mean.
Mean $\overline{X}=\frac{\sum X}{N}$.
We have
$\sum X=11+13+15+18+20+21+26=124$ and $N=7$.
Therefore
$MeanX=\frac{\sum X}{N}=\frac{124}{7}\approx 17.7$.