Here are direct links to some old chi-square blog postings. This one discusses the reversibility error and how properly to read an SPSS printout of a chi-square analysis. The other one illustrates the null hypothesis for chi-square analyses in terms of equal pie-charts.
The following photo of the board, containing chi-square tips, was added on November 15, 2011 (thanks to Selen).
Plus a song (added November 1, 2011):
One Degree is Free
Lyrics by Alan Reifman
(May be sung to the tune of “Rock and Roll is Free,” Ben Harper)
Look at your, chi-square table,
If it is, 2-by-2,
One cell can be filled freely,
While the others take their cue,
The formula that you can use,
Come on, from the columns, lose one,
And one, as well, from the rows,
Multiply the two, isn’t this fun?
One degree is free, in your table,
With con-tin-gen-cy, in your table,
One degree is free, in your table,
…free in your table,
…free in your table,
Say, your table is larger,
Maybe it’s 2-by-4,
Multiply one by three,
3 df are in store,
The df’s are essential,
To check significance,
Go to your chi-square table,
And find the right instance,
Three degrees are free, in your table,
With con-tin-gen-cy, in your table,
Three degrees are free, in your table,
…free in your table,
…free in your table,
(Guitar Solo)
