Statistics — Chapter Summary

Mean is the sum of all

Mean is the sum of all scores divided by the total number of scores. For grouped data, class marks are used, so the result is approximate. The direct

Choose a convenient value A as

Choose a convenient value A as assumed mean, find deviations d = x - A, and use X̄ = A + d̄. Taking any score or any convenient number as A does not c

First find d_i = x_i

First find d_i = x_i - A, then divide by the G.C.D. g to get u_i = d_i / g. Use X̄ = A + ū·g. This method reduces calculations further.

Median is the middle value when

Median is the middle value when scores are arranged in ascending order. If the number of scores is odd, the (n+1)/2 th score is the median. If the num

If class intervals do not fit

If class intervals do not fit scores properly, classes must be made continuous. Reduce each lower class limit by 0.5 and increase each upper class lim