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StatiCal User Manual
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The MxN Xtab key: Chi-square analysis of any size cross-tab table
The Fisher Exact test gets incredibly difficult for cross-tab tables larger than 2x2, and I won’t
attempt to perform that test on those tables. But cross-tab tables of any size can be analyzed
quickly and easily by the Chi-square test.
To use the MxN Xtab key, you first enter the cell counts of the table. Enter them in “row order”;
that is, enter all the numbers in the first row, then all the numbers in the second row, etc. Don’t
enter them column-wise, or you’ll get the wrong answer.
After entering all the cell counts, you have to enter two more numbers, to tell StatiCal how
many rows and how many columns the table has.
So, for example, Suppose you want to perform a chi-square test on the following 2-by-3 table,
showing the dessert preferences of a sample of males and females:
Pie Cake Jello
Male
15
20
23
Female 13
12
5
You would do it this way:
this key sequence
gives this result
Num, 15, Enter, 20, Enter, 23, Enter, 13, Enter, 12, Enter, 5, Enter, Chi Sq 5.3456
2, Enter, 3, Test, MxN Xtab
df
2.0000
p Val 0.0690
So this table indicates that there is no significant association between the gender and the dessert
preference (p = 0.069).
The Ord Xtab key: Analysis of a cross-tab of ordinal categories
The Chi-square and Fisher Exact tests assume that the rows and columns represent nominal
categorical variables; that is, categories whose values don’t fall into any natural, logical sequence,
like the following:
• Cauc, AfrAm, Asian, Other
• Pie, Cake, Jello
The sequence is unimportant, and switching the rows around, or switching the columns around
doesn’t affect the p-value from either the Chi-square or Fisher Exact test.
But many categorical variables are ordinal; that is, they do fall into a logical sequence:
• Neonate, Infant, Child, Adolescent, Adult, Geriatric
• Extra Small, Small, Medium, Large, Extra Large
• Emaciated, Normal, Overweight, Obese, Morbidly Obese
• Absent, Slight, Moderate, Loaded
• Strongly Disagree, Disagree, No Opinion, Agree, Strongly Agree
• Cured, Improved, No Change, Worse, Died
Updated March 21, 2014