A polling organization conducts a poll by making a random survey and is willing to accept a margin of error of 4% at a confidence level of 95% using the rule of thumb for the margin of error.

Question

A polling organization conducts a poll by making a random survey and is willing to accept a margin of error of 4% at a confidence level of 95% using the rule of thumb for the margin of error. What should the sample size be?

Answer 1

This question simplifies to an algebraic problem based on the rule of thumb approximation. We interpret the sample size to mean the number of people that will be polled.

The rule of thumb gives us a way to relate the desired margin of error (4%) to the number of people required, "n".

So we have:

4% = 100/sqrt(n) %

If the rule of thumb equation is correct, then we need only solve for "n". Rearranging, we will get

sqrt(n) = 100%/4% = 25

n = 25^2 = 625