First of all: I'm mathematically challenged.
Question 1: I use the Pearson correlation coefficient to correlate people. As a real life example: I correlate those people by comparing the number of points they've given to movies. This works very well. Now I would like to correlate not 1 variable but multiple, e.g. correlate how much they like the individual actors. How should I do that? Just take the average of all n correlations?
Question 2: if person $A$ and $B$ correlate for 0.9 than that is better then $A$ and $C$ who correlate for 0.8. But what if I had e.g. 25 movies while comparing $A$ and $B$ and 100 while comparing $A$ and $C$, should I then still consider $A$ and $B$? Or is there some extra weighting formula for this?