My question might seem pretty dumb but I'm teaching statistics to myself and never had in school or uni. I use a book and I'm currently trying to learn the chapter about two-way tables with two categorical variables.

In the book, it is written that you can check if two categorical variables are dependent or independent by

**comparing their conditional probabilities**(which you can find when looking at the two-way table). However, on the next sites it is written that you

**compare the conditional probability to the marginal probability**to see whether two categorical variables are independent or not.

Now, what is true? Or are both methods right?

Thank you