Calculating Required Sample Size to Estimate Population Mean (Jump to: Lecture | Video )

We can calculate what sample size we will need in order for our confidence interval to have a certain margin of error.

Figure 1.

On the verbal section of the SAT, the standard deviation is known to be 100. What size sample would we need to construct a 95% confidence interval with a margin of error of 20?

Figure 2.

We plug in the same "1.96" from the last example and find that a sample size of 97 is needed to create a 95% confidence interval with a margin of error of 20.