There must be

What I've got so far is that they are (1) based on chi-squared and the X^2 value is calculated with the expectation that the variables are independent of each other {i.e., not associated}, (2) phi {for 2x2 tables} is the square root of X^2 divided by the total number of observations {Cramer's V, for bigger tables, is slightly more complicated, with a diviision also by the lesser of rows or columns minus one.} and that the possible range is 0 to 1. So how can I get phi values > 1?

Say the question is assocation between a particular surname and Y-DNA matches. The surname has a frequency within the population of 0.3% {making it one of the more common}; the random-chance expected frequency would be 0.003. Observation of whether Y-DNA matches agree with the surname or disagree are 147 agree and 648 disagree, for a total of 795 matches. That gives us a table like this:

- - - - - - Observed - - Expected - - (O-E)^2/E

Agree - - - 147 - - - - - - - 3 - - - - - 6912

Disagree - - 648 - - - - - 792 - - - - - - 26

Total - - - - 795- - - - - - 795 - - - - - 6938

Phi = SQRT(X^2/n) = SQRT(6938/795) = 2.95 ???

Thanks in advance for helping me see where I've gone wrong.

-rt_/)

**something**I'm not getting with these measures of association for nominal variables. Please help me understand.What I've got so far is that they are (1) based on chi-squared and the X^2 value is calculated with the expectation that the variables are independent of each other {i.e., not associated}, (2) phi {for 2x2 tables} is the square root of X^2 divided by the total number of observations {Cramer's V, for bigger tables, is slightly more complicated, with a diviision also by the lesser of rows or columns minus one.} and that the possible range is 0 to 1. So how can I get phi values > 1?

Say the question is assocation between a particular surname and Y-DNA matches. The surname has a frequency within the population of 0.3% {making it one of the more common}; the random-chance expected frequency would be 0.003. Observation of whether Y-DNA matches agree with the surname or disagree are 147 agree and 648 disagree, for a total of 795 matches. That gives us a table like this:

- - - - - - Observed - - Expected - - (O-E)^2/E

Agree - - - 147 - - - - - - - 3 - - - - - 6912

Disagree - - 648 - - - - - 792 - - - - - - 26

Total - - - - 795- - - - - - 795 - - - - - 6938

Phi = SQRT(X^2/n) = SQRT(6938/795) = 2.95 ???

Thanks in advance for helping me see where I've gone wrong.

-rt_/)

Last edited: