Question

How would you find out how many sixth through eighth grade students are interested in joining a running club?

Answer 1

The question is incomplete. The complete question is :

How would you find out how many sixth through eighth grade students are interested in joining a running club? Explain how to choose a sample that will give you a good representation of a whole population.

Answer :

the sample should be random

Explanation :

We have to find the number of student from 6th through 8th grade students those who wanted to join a running club by choosing a sample of population. So in order to choose a sample which will provide a good representation for the whole population is that the sample must be a $\text{random sample}$ from  $\text{entire set of students }$ and it should also include enough students to be reliable. The smaller samples have a more variation that lead to a lesser reliable inference.