Question

A sample size of n = 20 is a simple random sample selected from a normally distributed population. Find the critical value ta/2 corresponding to a 95% confidence level. I know the answer is 2.093, but I'm not sure how to get there. Can anyone show me?

Answer 1

The above picture shows you what you need to look up. The degrees of freedom is one less than the sample size. Significance level is 1-confidence level=1-0.95=0.05. t(ɑ/2) signifies 2-tail because half the significance level is in the left tail of the normal distribution and half in the right tail.