gives you 2.82, which tells you that to get an SE of 5, you need

, or about 56 participants.

And because we assume you took our advice, we’ll assume you’ve already recruited the first 20

participants for your pilot study. Now, you only have to recruit only another 36 participants to have a

total of 56.

Admittedly, this estimation is only approximate. But it does give you at least a ballpark idea of

how big your sample size needs to be to achieve the desired precision.