On Apr 16, 2:01 pm, Ray Koopman <koop...@[EMAIL PROTECTED]
> wrote:
> On Apr 15, 5:54 pm, ouyang....@[EMAIL PROTECTED]
wrote:
>
>
>
> > On Apr 15, 7:33 pm, Richard Ulrich <Rich.Ulr...@[EMAIL PROTECTED]
> wrote:
> >> On Tue, 15 Apr 2008 11:28:19 -0700 (PDT), ouyang....@[EMAIL PROTECTED]
wrote:
> >>> Hi,
> >>> I am new to statistics. I got couple questions about chi square and
g
> >>> independence test. For chi square test, how do I handle all zero
> >>> columns in cross tables? Should those columns be included in the
> >>> table? all zero columns will give zero expectation for cells in
those
> >>> columns and cause divided by zero errors.. For g test, what to do if
> >>> some cells have zero observations? That will cause log of zero
error.
>
> >> For the ordinary contingency table, you drop
> >> any rows or columns that total zero.
>
> >> --
> >> Rich Ulrich
>
> >>http://www.pitt.edu/~wpilib/index.html
>
> > Thank you. How about zero cells in G test?
>
> Individual zero cells are no problem -- they give 0 mathematically,
> with no special treatment necessary, because x log x -> 0 as x -> 0.
> Think of it as (log x)/(1/x). Both log x and 1/x -> infinity as x ->
> 0, but 1/x gets bigger faster.
Got it. Thanks.
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