Find the value of a 90% confidence interval when the sample size is 25?

Answer 1

Step 1: Subtract 1 from your sample size. 25– 1 = 25. This gives you degrees of freedom, which you’ll need in step 3.

Step 2: Subtract the confidence level from 1, then divide by two. 

(1 – .90) / 2 = .05

Step 3: Look up your answers to step 1 and 2 in the t-distribution table. For 24 degrees of freedom (df) and α = 0.05, my result is 1.711.