Calculating Critical Values of t-Distributions Using Tables of Percentage Points Refer to: Table of Percentage Points of the t Distribution, p. 3 of this document. Two-Tailed Critical Values of the t-Distribution Two-tailed 5 percent critical values of the t distribution: α = 0.05 ⇒ α/2 = 0.025. •
Locate column of table headed t0.025 lies between
0.025 ← area in one tail of t-distribution 0.05 ← area in two tails of t-distribution
t0.025 = 2.000
t0.025 = 1.980.
t0.025 can be approximated using the following linear interpolation formula: