I am taking quantum mechanics without having officially taken stats, and although most of it makes sense so far, I am having trouble understanding what to do in this situation: I have two data sets initially of the same size. I take only the numbers in both sets that are greater than 0.95 and analyze them to find correlation. (This is to introduce us to Berkson's Paradox). However, the number of numbers over 0.95 is 45 in one set and 48 in another. For the equations we were given to help determine correlation, we need to sum the element-wise product of these two unequal sets. How should I handle this? Should I just consider the first 45 elements of the larger set?