Thursday, June 9, 2011

Minitab - Cross Tabulation and Chi-Square

GP is sending a set of discrete data and ask for help to test for significant differences. Looking at the data, I know Chi Square or Contingency Table should be the right analysis tool to test the data. But… OMG, I can’t remember how to run it in Minitab.
Honestly, it takes me few days to do the treasure hunt in the Google. Finally, I got the answer.
Hmmm… I think I should document it for my future reference.

Here the Minitab step by step that I copy down ( Minitab Ref ID 210 )

Step 1 : Tabulate the data as below
                                Pass       Fail
B.Improve                3788       52
A.Improve                3835       5

Step 2 : Stack the row ( Data > Stack > Row )
Store stacked data in, C6.
Store row subscripts in,  C4.
Store column subscripts in, C5.
Click OK.

Step 3 : Stat > Tables > Cross Tabulation and Chi-Square
For rows, enter C4.
For columns, enter C5.
In Frequencies are in, enter C6.

Step 4 : Display. Check all the 4
Count
Row percents
Column percents
Total percents

Step 5 : Other Stats.
Check Fisher's exact test for 2x2 tables. Click OK in each dialog box.

Step 6 : Chi-Square
Check Chi-Square analysis

Finally, this is the answer I get.

Tabulated statistics: C4, C5

Using frequencies in C6


Rows: C4   Columns: C5

         Fail    Pass      All

1          52    3788     3840
         1.35   98.65   100.00
        91.23   49.69    50.00
        0.677  49.323   50.000

2           5    3835     3840
         0.13   99.87   100.00
         8.77   50.31    50.00
        0.065  49.935   50.000

All        57    7623     7680
         0.74   99.26   100.00
       100.00  100.00   100.00
        0.742  99.258  100.000

Cell Contents:      Count
                    % of Row
                    % of Column
                    % of Total


Pearson Chi-Square = 39.044, DF = 1, P-Value = 0.000
Likelihood Ratio Chi-Square = 45.424, DF = 1, P-Value = 0.000


Fisher's exact test: P-Value =  0.0000000

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