Print details of a chi-squared test

Prints out the details of the computations involved in a chi-squared test on a table. Includes the expected values and the chi-squared contribution of each cell.

chisq.detail(tab)

Arguments

tab

Matrix or table to be analyzed

Details

This function prints out the input table along with the expected value for each cell under the null hypothesis. It also prints out the chi-squared contribution of each cell in the same pattern as the table. This shows the computations involved and one rule of thumb is to look for these values that are greater than 4 as a post-hoc analysis.

Value

This function is used primarily for its side effect of printing the results, but does return invisibly a list with the following components:

obs

A matrix of the observed values, same as tab.

expected

A matrix of the expected values under the null hypothesis.

chi.table

A matrix of the chi-squared contributions of each cell.

chi2

The chi-squared test statistic.

References

~put references to the literature/web site here ~ Moore, bps

Author

Greg Snow, 538280@gmail.com

See also

chisq.test,loglin, xtabs, table, prop.table, CrossTable from the gmodels package.

Examples

chisq.detail(HairEyeColor[,,1])
#> 
#> 
#> observed
#> expected
#> 
#>       Brown   Blue Hazel Green Total
#> Black 32     11    10     3       56
#>       19.67  20.27  9.43  6.62      
#>                                     
#> Brown 53     50    25    15      143
#>       50.23  51.77 24.09 16.91      
#>                                     
#> Red   10     10     7     7       34
#>       11.94  12.31  5.73  4.02      
#>                                     
#> Blond  3     30     5     8       46
#>       16.16  16.65  7.75  5.44      
#>                                     
#> Total 98    101    47    33      279
#> 
#> 
#> Cell Contributions
#>       Brown    Blue   Hazel   Green        
#> Black  7.73 +  4.24 +  0.03 +  1.98 +      
#> Brown  0.15 +  0.06 +  0.03 +  0.22 +      
#> Red    0.32 +  0.43 +  0.28 +  2.21 +      
#> Blond 10.71 + 10.70 +  0.98 +  1.20 = 41.28
#> 
#> df = 9  P-value = 0 
#> 
chisq.detail(HairEyeColor[,,2])
#> 
#> 
#> observed
#> expected
#> 
#>        Brown   Blue Hazel Green Total
#> Black  36      9     5     2       52
#>        20.27  18.94  7.64  5.15      
#>                                      
#> Brown  66     34    29    14      143
#>        55.74  52.08 21.02 14.16      
#>                                      
#> Red    16      7     7     7       37
#>        14.42  13.48  5.44  3.66      
#>                                      
#> Blond   4     64     5     8       81
#>        31.57  29.50 11.90  8.02      
#>                                      
#> Total 122    114    46    31      313
#> 
#> 
#> Cell Contributions
#>       Brown    Blue   Hazel   Green         
#> Black 12.21 +  5.22 +  0.91 +  1.93 +       
#> Brown  1.89 +  6.28 +  3.03 +  0.00 +       
#> Red    0.17 +  3.11 +  0.45 +  3.04 +       
#> Blond 24.08 + 40.34 +  4.00 +  0.00 = 106.66
#> 
#> df = 9  P-value = 0 
#>