I am trying to measure the correlation between two binary categorical variables. I tried in two ways.
Use the chi-square test for independence of two-way table. The p-value as the correlation.
Treat them as numerical variables with value of 0/1. Calculate the correlation between them.
The results are so different, the first gives 9.5e(-31) and the second gives around 0.3.
How to interpret these two correlations and why the difference can be so large?