if the critical t-value for a confidence interval calculation was 2.704 how big was the sample

Question

 I don't know what equation to use to solve this or what to plug into my calculator

Answer 1

Please note that without a standard deviation or the desired error, I can only give you a formula to use.

 

In confidence intervals, the error is always E = t_crit(σ/√n).  If we solve this for n, we get n=(t_critσ/E)².

 

For example, if the σ = 5 and the desired error E = 1.5, then the sample size would be

 

n = (2.704•5/1.5)² = 81.24 or 82.  Please note you always round up.