query re "Valid N (listwise)"

[earthman0...@hotmail.com]

Folks

In the descriptive statistics output, what does "Valid N (listwise)"
refer to? I'm just using default settings.

AA

[Lawrence]

Hi,

Valid N will show the number of non missing cases for the particular
variable. Assume you have more than one variable and your data set
contains 500 cases. Your first variable contains 495 valid cases and
the second contains 490 valid cases. Now you will get Valid
N(listwise) is 490. i.e., it will take the valid cases for both
variables. The following points from spssbase.pdf will also helpful
for you.

By default, DESCRIPTIVES deletes cases with missing values on a
variable-by-variable basis.
A case with a missing value for a variable will not be included in the
summary statistics for
that variable, but the case will be included for variables where it is
not missing.

When either the keyword VARIABLE or the default missing-value
treatment is used,
DESCRIPTIVES reports the number of valid cases for each variable. It
always displays the
number of cases that would be available if listwise deletion of
missing values had been
selected.

Thanks,

Lawrence

[Bruce Weaver]

The number of cases that have valid values for all of the variables
listed in your DESCRIPTIVES command.

--
Bruce Weaver
bwe...@lakeheadu.ca
www.angelfire.com/wv/bwhomedir
"When all else fails, RTFM."

[Richard Ulrich]

On Fri, 26 Oct 2007 03:01:20 -0700, Lawrence
<lawrenc...@gmail.com> wrote:

> Hi,
>
> Valid N will show the number of non missing cases for the particular
> variable. Assume you have more than one variable and your data set
> contains 500 cases. Your first variable contains 495 valid cases and
> the second contains 490 valid cases. Now you will get Valid
> N(listwise) is 490. i.e., it will take the valid cases for both
> variables. The following points from spssbase.pdf will also helpful
> for you.

- If the 10 missing do not overlap the other 5 missing,
you will get Valid N(listwise) of 485, not 490.

Some procedures, like factor analysis, will use only the
Valid N(listwise) cases, either by default or by requirement.
(Factor, by the way, didn't tell you its N, last time I looked.)

[snip, rest]

--
Rich Ulrich, wpi...@pitt.edu
http://www.pitt.edu/~wpilib/index.html

[earthman0...@hotmail.com]

On Fri, 26 Oct 2007 11:25:24 -0000, Bruce Weaver
<bwe...@lakeheadu.ca> wrote:

thank you all - makes perfect sense once it's explained!
regards
AA