**Mean, Mode, Median, AD, SD
**

**for**

**uniform frequency
distribution**

Increment to be zero or 1. Mean =ΣfX /N where f is frequency and X is the mid-point of scores in interval.

Median= L + ( N/2 - F)* i /fm where L is the exact lower limit of the class interval upon which the median lies, N is total no. of scores, F is sum of scores of all

intervals below L, fm is the frequency within the interval
upon which the median falls & i is the length of class interval. Mode=3*median -
2*Mean; Median, q1,q3 are that point in a frequency distribution below which lie
50% , 25% and 75% of the score respectively. Using the same methods by which the
median and the quartiles were found, one may compute points below which lie say
20%,38%,79% etc or any percent of the scores. These points are called
percentiles and designated by **P _{p}**. So

Coefficient of variation **γ **shows what %
the standard deviation is of the mean. It is useful in comparing the
variabilities of a group upon the same test administered under different
conditions such as a group of people working with and without distraction. Or it
may be used to compare two groups on the same test when the groups do not differ
greatly in mean.

When the intervals are wide & cumulative frequency N is small, grouping
errors are introduced because the scores in an interval are not always
distributed symmetrically about the mid point and the discrepancy becomes more
apparent when intervals are wide and N is small.Sheppard's correction is often
used to adjust the error. It is given by **σ _{c }**= √