[!TLDR] Find class midpoints, the weighted mean, then average $f_i|x_i-\bar x|$ over $N$. [!ANSWER] Mean …

The class midpoints are $x_i:5,15,25,35,45$ with frequencies $f_i:6,9,15,14,6$, so $N=6+9+15+14+6=50$. Now $\sum f_ix_i=5(6)+15(9)+25(15)+35(14)+45(6)=30+135+375+490+270=1300$, giving $\bar x=\dfrac{1300}{50}=26$. The absolute deviations $|x_i-26|$ are $21,11,1,9,19$, and weighting by frequency: $f_i|x_i-\bar x|=6(21)+9(11)+15(1)+14(9 …

Find the class midpoints and the frequency-weighted mean, form the absolute deviation of every midpoint from the mean, w …

A common mistake is using the class width or the class limits instead of the class midpoint $x_i=\frac{\text{low …