[R] help please. 2 tables, which test?

[R. Michael Weylandt]

You should probably read up on what the chi-squared test actually
tests: in one form, it asks whether some set of observations could
have come from a given multinomial distribution. Concretely, it asks
whether it is "reasonable" to get 3 blues, 4 reds, and 2 whites from a
uniform distribution over read white and blue. (Real statisticians
will have all sorts of problems with that over-simplification) What
you seem to be asking is whether it is "reasonable" to get 3 blues 4
reds, 2 whites, and 6 greens from a uniform distribution over red
white and blue -- obviously something doesn't fit here. Caveat: if
matrix1 matches matrix2 but there were null observations that got
dropped, then this can be done.

https://en.wikipedia.org/wiki/Pearson%27s_chi-squared_test

The website http://stats.stackexchange.com/ can (and will) provide
more statistically oriented help.

Michael

On Fri, Mar 9, 2012 at 11:46 AM, aoife doherty <aaral.singh at gmail.com> wrote:
> Thank you. Can the chi-squared test compare two matrices that are not the
> same size, eg if matrix 1 is a 2 X 4 table, and matrix 2 is a 3 X 5 matrix?
>
>
> On Fri, Mar 9, 2012 at 4:37 PM, Greg Snow <538280 at gmail.com> wrote:
>
>> The chi-squared test is one option (and seems reasonable to me if it
>> the the proportions/patterns that you want to test).  One way to do
>> the test is to combine your 2 matrices into a 3 dimensional array (the
>> abind package may help here) and test using the loglin function.
>>
>> On Thu, Mar 8, 2012 at 5:46 AM, aaral singh <aaral.singh at gmail.com> wrote:
>> > Hi.Please help if someone can.
>> >
>> > Problem:
>> > I have 2 matrices
>> >
>> > Eg
>> >
>> > matrix 1:
>> >                Freq  None  Some
>> >  Heavy    3        2          5
>> >  Never    8       13         8
>> >  Occas    1        4          4
>> >  Regul     9        5         7
>> >
>> > matrix 2:
>> >                  Freq     None     Some
>> >  Heavy        7          1             3
>> >  Never      87         18          84
>> >  Occas      12           3            4
>> >  Regul        9            1            7
>> >
>> >
>> > I want to see if matrix 1 is significantly different from matrix 2. I
>> > consider using a chi-squared test. Is this appropriate?
>> > Could anyone advise?
>> > Many thank you.
>> > Aaral Singh
>> >
>> > --
>> > View this message in context:
>> http://r.789695.n4.nabble.com/help-please-2-tables-which-test-tp4456312p4456312.html
>> > Sent from the R help mailing list archive at Nabble.com.
>> >
>> > ______________________________________________
>> > R-help at r-project.org mailing list
>> > https://stat.ethz.ch/mailman/listinfo/r-help
>> > PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> > and provide commented, minimal, self-contained, reproducible code.
>>
>>
>>
>> --
>> Gregory (Greg) L. Snow Ph.D.
>> 538280 at gmail.com
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
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>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.