Afinite population consists of four elements: 6, 1, 5, 3. (a) how many different samples of size n = 2 can be selected from this population if you sample without replacement? (sampling is said to be without replacement if an element cannot be selected twice for the same sample.)

Since the order of elements doesn't matter, we use the formula for combination as follows.



So the number of ways to choose 2 elements from a set of 4 elements would be


Thus the answer is 6. 

First step is to get rid of the square root. remember that a square root is the same as raising to the (1/2) power. see below: multiply exponents per exponent rules to get: remember you subtract exponents from the denominator and add exponents in the numerator so: simplify further: so a is the correct choice. if you don't understand this google exponent rules and it will you understand. look at the image results.