|Date: ||Mon, 18 May 1998 11:07:40 -0500|
|Reply-To: ||Rick Oliver <richard@SPSS.COM>|
|Sender: ||"SPSSX(r) Discussion" <SPSSX-L@UGA.CC.UGA.EDU>|
|From: ||Rick Oliver <richard@SPSS.COM>|
|Organization: ||SPSS Inc.|
|Subject: ||Re: normality|
|Content-Type: ||text/plain; charset=us-ascii|
Patricia Anne O'connell wrote:
> I have a number of variables which are not normally distributed. Spss
> gives statistics for skewness and kurtosis. However, I am not sure what
> these numbers mean.
> Any help would be appreciated.
In SPSS 8.0 for Windows, right-clicking on the label "Skewness" in a
pivot table, provides the following definition:
"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 long left tail. A skewness value
greater than 1 generally indicates a distribution that differs
significantly from a normal distribution."
For kurtosis, the following is provided:
"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 that 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
These definitions can also be found using the searchable index in the
online help system.