Question

The following data are the heights of four students in centimeter; 110, 125, 120, and 130. Suppose sample size of 2 is to be taken from the population of four students. What will be the probability when the sample mean is 115?

Answer 1

The table with all samples of size 2 (without replacement) and their means is presented below:

As we can see mean $115$ occurs once in a table. There are $6$ samples. It means, that the probability of this mean is $\frac16$.