Hi Arun, this is a really good question. I assume you refer to Pearson’s Chi-Square test (see its Wikipedia page). As you can see, Pearson’s Chi-Square test requires that you have some theoretical knowledge of the variable you’re examining — you’re basically comparing the actual given results of sampling to the ones you believed you’ll get. Cramer’s V and Thiel’s U require no such knowledge — they compare two different variables.