30, 32, 34, 36, 38, 40, 42 = 7 terms
Assumed mean = \(\frac{30 + 32 + 34 + 36 + 38 + 40 + 42}{7}\)
\(\frac{252}{7}\) = 36
Next we minus each value from the mean (36). Hence we have;
x x - \(\mu\) x - \(\mu\)
30 -6 6
32 -4 4
34 -2 2
36 0 0
38 2 2
40 4 4
42 6 6
Total 24
M.D = \(\sum\) \(\frac{|x - \mu |}{N}\) = \(\frac{24}{7}\) = 3.42