I have a several variables. I have a set of experiments which indicate whether each of these variables has a positive signal in the experiments or not. I need to identify what subset of the variables which is mostly correlated with each other in the subset. I know we can do correlation analysis to test the relationship between two variables. How to do this to test the relationship of multiple variables together, at once?
I recommend you read this Multiple Correlation. There are useful formulas, proofs and examples (but only in Excel). I think, that's a good post to understand multiple correlation.