How to Find a Critical T Value with T.INV.2T in Excel

Use T.INV.2T to get the critical t value for a small sample, build an interval and make a pass/fail call.

You will learn to

• Find the two-tailed critical t value
• Use it to build an upper confidence limit
• Compare a t-score with the critical value to make a decision

How it works

T.INV.2T returns the critical t value for a two-tailed test or a two-sided confidence interval. Pass the significance level (5% for 95% confidence) and the degrees of freedom, usually the sample size minus 1. With 10 measurements, =T.INV.2T(5%,9) returns about 2.262.

Multiply the critical value by the standard error (SD ÷ √n) to get a margin of error, or compare it with a t-score: if the absolute t-score is larger than the critical value, the result is statistically significant at that level.

=T.INV.2T(0.05,9)