Adding too many variables to a regression model

[Joe Tuckles]

Am I correct in thinking adding too many variables to a regression model can increase the likelihood of overfitting the model, reducing statistical power and increasing the chances of error? Are there references to show this?

[Carlo Lazzaro]

Joe:
see Frank Harrel's excellent textbook on Regression Modelling Strategies (2nd ed): https://www.springer.com/gp/book/9783319194240 pages 72-74.

[Alex Williams]

I concur that book is a very useful resource.

[Carlo Lazzaro]

I wrote Harrel but meant Harrell (I beg your pardon Frank, should you ever come across this post).