Math & Science
T-Test Calculator
Compare means between groups
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Frequently asked questions
Independent vs paired?
Use paired for before/after measurements on same subjects. Independent for different groups.
One-tailed vs two-tailed?
One-tailed if you predict direction of difference. Two-tailed if either direction possible.
What is effect size?
Cohen's d measures practical significance. 0.2=small, 0.5=medium, 0.8=large.
Related tools
About this tool
Inputs
- Group 1 Data
- Group 2 Data
- Test Type
- Tails
- Independent
- Paired
- One-tailed
- Two-tailed
Results
- T-Statistic
- P-Value
- Degrees of Freedom
- Conclusion
- Cohen's d
- Statistically significant
- Not significant
Quick mental math is convenient, but it introduces errors. The T-Test Calculator eliminates that risk by computing the exact result from your inputs. You supply group 1 data, group 2 data, test type, tails, independent, paired, one-tailed and two-tailed, and the tool calculates t-statistic, p-value, degrees of freedom and other key metrics from those figures. Visualizing a mathematical relationship often makes the result more intuitive than the raw number alone. Percentage change is computed as (new − old) / old × 100, one of the most universally useful formulas.
Having a dedicated tool to compare means between groups saves time you would otherwise spend searching for formulas or setting up a spreadsheet. When in doubt, estimate the answer first so you have a sanity check for the exact result. Cohen's d measures practical significance. 0.2=small, 0.5=medium, 0.8=large. Precision matters: rounding at intermediate steps can introduce errors that compound in multi-step calculations. Run the calculation with your best-case and worst-case assumptions to bracket the likely outcome.