Correlation analysis of Nominal data with ChiSquare Test in Data Mining
ChiSquare Test
This analysis can be done by the chisquare test.A chisquare test is the test to analyze the correlation of nominal data.
Correlation VS Causality:
Correlation does not always tell us about causality.
Example:
 The number of students passed in exam and number of car theft in a country is correlated with each other butÂ maybe it does not mean that the number of students passed effects car theft in a country.
But in some cases it may be;
 The number of students passed in the exam and the number of students who live near to the university is correlated with each other and maybe a number of students who live near to the university can be a cause of the student result.
[quads id=2]
Â  Passed student  Not passed student  Sum 
Live near University  Observed=140
Expected = 180*330/1320 Expected =45 
Observed=190
Expected = 1140*330/1320 Expected =285 
330 
Not live near University  Observed=40
Expected = 180*990/1320 Expected =135 
Observed=950
Expected = 1140*990/1320 Expected =855 
990 
Sum  140 + 40 =Â 180  190 + 950 = 1140  1320 
Degrees of freedom:
DF = (r – 1) * (c – 1)
Level of significance:
.01  .05  .10 
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