I am having really hard time finding a citable source for the method described in the following link: Correlation between a nominal (IV) and a continuous (DV) variable. I found this method very useful and want to cite a peer-reviewed source. So far, I found the following:
(1) Salkind, Neil, ed. Encyclopedia of Research Design. Sage, 2010. pp. 422-425 https://methods.sagepub.com/Reference/encyc-of-research-design/n133.xml
(2) Witte, Robert S, John S. Witte. Statistics. Wiley, 2017. pp. 308-311 https://www.google.com/books/edition/Statistics/QpBEDwAAQBAJ?hl=en&gbpv=1&dq=S.+Witte.+Statistics&printsec=frontcover
However, the references above are about how to interpret ETA squared without discussing ways to fit categorical variables.
What I am looking for is something like this:
Cohen, Yosef, Jeremiah Y. Cohen. Statistics and Data with R: An Applied Approach Through Examples. Wiley, 2008.
The problem with this book is that it does not discuss ETA-squared as a measure of strength of association between a categorical independent variable and a continuous dependent variable.
I have searched more than 20 academic books but no success yet. I am new to this field, so maybe I am looking at wrong places. A non-peer-reviewed source that might be close to the method described by @Silverfish (users/22228) is the following: