User Guide

341
Summarize
Harmonic Mean. Used to estimate an average group size when the sample sizes in the
groups are not equal. The harmonic mean is the total number of samples divided by
the sum of th
e reciprocals of the sample sizes.
Kurtosis. A measure of the extent to which observations cluster around a central point.
For a normal distribution, the value of the kurtosis statistic is 0. Positive kurtosis
indicates t
hat the observations cluster more and have longer tails than those in the
normal distribution and negative kurtosis indicates the observations cluster less
and have shorter tails.
Last. Disp
lays the last data value encountered in the data file.
Maximum. Thelargestvalueofanumericvariable.
Mean. A measure of central tendency. The arithmetic average; the sum divided
by the numb
er of cases.
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 a
re 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.
Minimum.
The smallest value of a numeric variable.
N. The number of cases (observations or records).
Percent of Total N. Percentage of the total number of cases in each category.
Percent o
f Total Sum.
Percentage of the total sum in each category.
Range. The difference between the largest and smallest values of a numeric variable;
the maximum minus the minimum.
Skewness
.
A measure of the asymmetry of a distribution. The normal distribution is
symmetric and has a skewness value of zero. A distribution with a significant positive
skewness has a long right tail. A distribution with a significant negative skewness
has a lon
g left tail. As a rough guide, a skewness value more than twice its standard
error is taken to indicate a departure from symmetry.
Standard Error of Kurtosis. The ratio of kurtosis to its standard error can be used as a
test of n
ormality (that is, you can reject normality if the ratio is less than -2 or greater
than +2). A large positive value for kurtosis indicates that the tails of the distribution