User Guide

310
Chapter 13
Frequencies
Statistics
Figure 13-3
Frequencies Statistics dialog box
Percentile Values. Values of a quantitative variable that divide the ordered data
into groups so that a certain percentage is above and another percentage is below.
Quartiles (the 25th, 50th, and 75th percentiles) divide the observations into four
groups of equal size. If you want an equal number of groups other than four, select
Cut points for n equal groups. You can also specify individual percentiles (for example,
the 95th percentile, the value below which 95% of the observations fall).
Central Tendency. Statistics that describe the location of the distribution include the
mean, median, mode, and sum of all the values.
 Mean. A measure of central tendency. The arithmetic average; the sum divided by
thenumberofcases.
 Median. The value above and below which half the cases fall, the 50th percentile.
If there is an even number of cases, the median is the average of the two middle
cases when they are sorted in ascending or descending order. The median is a
measure of central tendency not sensitive to outlying values--unlike the mean,
which can be affected by a few extremely high or low values.
 Mode. The most frequently occurring value. If several values share the greatest
frequency of occurrence, each of them is a mode. The Frequencies procedure
reports only the smallest of such multiple modes.
 Sum. The sum or total of the values, across all cases with nonmissing values.