T Test Calculator
Calculate test with our free science calculator. Uses standard scientific formulas with unit conversions and explanations.
Reviewed by Daniel Agrici, Founder & Lead Developer
Reviewed by Daniel Agrici, Founder & Lead Developer
Formula
t = (x̄₁ - x̄₂) / √(s₁²/n₁ + s₂²/n₂) | Welch's df ≈ (s₁²/n₁ + s₂²/n₂)² / [(s₁²/n₁)²/(n₁-1) + (s₂²/n₂)²/(n₂-1)]
Welch's t-test compares means of two groups with possibly unequal variances. The t-statistic measures the difference relative to combined standard error. Degrees of freedom are approximated using Welch-Satterthwaite.
Worked Examples
Example 1: Two group comparison
Problem:Group 1: mean=25, SD=5, n=30. Group 2: mean=22, SD=4, n=30
Solution:t = 3/(√(25/30+16/30)) = 3/1.170 = 2.564. df≈55.7. p≈0.013
Result:t = 2.56, p ≈ 0.013 — Significant
Reviewed by Daniel Agrici, Founder & Lead Developer · Editorial policy