ABSTRACT
The mean, median and modal values for grouped data may be determined from a histogram. The median value is obtained by selecting a variable value such that the area of the histogram to the left of a vertical line drawn through the selected variable value is equal to the area of the histogram on the right of the line. The median is the value of time corresponding to a vertical line dividing the total area of the histogram into two equal parts. The standard deviation of a set of data gives an indication of the amount of dispersion, or the scatter, of members of the set from the measure of central tendency. For grouped data the give may be used to determine the quartile values. When a set contains a large number of members, the set can be split into ten parts, each containing an equal number of members.
