41 . This frequency distribution represents the commission earned ( in dollar ) by 100 salespeople employed at several branches of a large chain store . ( Using D - Method ) Class Frequency Cumulative Relative\\ Frequency Mid - point ( x ) of dZ d e f 150 - 158 5 5 0. 05 154 3 - 15 2 25 1125 159 - 167 16 21 0 . 21 163 - 2 - 32 1024 16384 168 - 176 20 41 0. 41 17 2 - 1 - 20 4UU 8000 177- 185 21 62 0. 62 181 O U 186 -194 20 82 0. 82 190 - 20 400 8000 195 - 203 15 97 0. 97 199 2 30 90 0 13500 204- 212 3 100 1. 00 108 3 9 81 243 Total 100 100 1 . 00 1167 O - 48 3030 47252 a ) Mean b ) Median sum of FX / sum of f = 17728 / 100 = 177 . 28 C ) Mode d) Range @ ) Variance D) Standard deviation 8 ) 310 Quartile*