Since this is a combination not a permutation problem, (order does not matter) you should use the "n choose k" formula.
C=n!/(k!(n-k)!) where C is the number of unique combinations, n equals the total number of possible choices and k equals the specific number of choices. In this case:
C=9!/(4!(9-4)!)
C=9!/(4!5!)
C=362880/(24*120)
C=362880/2880
C=126
So there are 126 unique ways to pick 4 people from a group of 9 people.
Often, variability is most usefully expressed in the same units as the original data. That's what <em>standard deviation</em> (square root of variance) does. In situations where that is the case, the variance is useful only for getting to the value of standard deviation.
Answer is (4,-3) I’m pretty sure it’s right sorry if it’s wrong
