Sry can't answer your question but I'll keep trying to figure it out :(
ANSWER

EXPLANATION
We want to evaluate

Use indices to rewrite the expression as:

We know that

So we rewrite the expression to obtain;

This gives us;

This simplifies to


Statistics is not an exact science, meaning that with any answer, there will be variance. This is because the sample size used to obtain values is always smaller than the population being studied.