Combinations Worksheets

What Are Statistical Combinations? When you are in the middle of statistical experiments, finding the total number of points in a sample can be hard or tedious. Thus, to make the counting task much easier, there are a few methods that can save us both time and effort. One of those methods is known as combinations. Combinations are a selection of the part of or all of a set of objects without considering the order in which these objects are selected. For instance, if we have three letters, X, Y and Z, then you can ask in how many ways you can select 2 letters from the set. To put it generally, n number of objects can be arranged in the form of n(n-1)(n-2)...(n – r + 1)/r! = n!/r!(n-r)! = _nCr. Now, if we consider our example, there are three letters, X, Y, Z, then, n is 3, while r is 2 for this problem. The number of combinations is 3C2 = 3! / 2!(3 - 2)! = 3! /2!1! = (3)(2)(1)/(2)(1)(1) = 3.