Thank you for the replies.
So what my test wants to do is this:

I have a big matrix, 30 rows (students in a class) X 50 columns (students
grades for the year).
An example of the matrix is as such:


                    grade1       grade2        grade3     .....  grade 50
student 1
student 2***
student 3
student 4***
student 5***
student 6
.
.
.
.
.
student 30***

As you can see, four students (students 2,4,5 and 30) have stars beside
their name. I have chosen these students based on a particular
characteristic that they all share.I then pulled these students out to make
a new table:

                    grade1          grade2         grade3 ....... grade 50

student 2
student 4
student 5
student 30


and what i want to see is basically is there any difference between the
grades this particular set of students(i.e. student 2,4,5 and 30) got, and
the class as a whole?

So my null hypothesis is that there is no difference between this set of
students grades, and what you would expect from the class as a whole.

Aaral






On Sat, Mar 10, 2012 at 12:18 AM, Greg Snow <538280@gmail.com> wrote:

> Just what null hypothesis are you trying to test or what question are
> you trying to answer by comparing 2 matrices of different size?
>
> I think you need to figure out what your real question is before
> worrying about which test might work on it.
>
> Trying to get your data to fit a given test rather than finding the
> appropriate test or other procedure to answer your question is like
> buying a new suit then having plastic surgery to make you fit the suit
> rather than having the tailor modify the suit to fit you.
>
> If you can give us more information about what your question is we
> have a better chance of actually helping you.
>
> On Fri, Mar 9, 2012 at 9:46 AM, aoife doherty <aaral.singh@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@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@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@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@gmail.com
> >>
> >> ______________________________________________
> >> R-help@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@gmail.com
>
> ______________________________________________
> R-help@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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