Calculator
Raw data overrides summary values when at least two numeric values are entered.
Formula Used
For a one sample or paired test, the statistic is t = (mean - null value) / (s / sqrt(n)). Degrees of freedom are n - 1.
For a pooled two sample test, sp² = ((n1 - 1)s1² + (n2 - 1)s2²) / (n1 + n2 - 2). Then SE = sp sqrt(1/n1 + 1/n2).
For Welch testing, SE = sqrt(s1²/n1 + s2²/n2). Degrees of freedom use the Welch Satterthwaite approximation. The p value comes from the t distribution.
How to Use This Calculator
- Select the correct test type for your study design.
- Choose a two tailed, right tailed, or left tailed test.
- Enter alpha, the hypothesized value, and summary statistics.
- Paste raw data if you want the tool to compute means and standard deviations.
- Press Calculate to show the result above the form.
- Use CSV or PDF buttons to save the calculation.
Example Data Table
| Case | Test type | Sample 1 | Sample 2 or null | Suggested tail |
|---|---|---|---|---|
| Compare class score with 70 | One sample | n 16, mean 74.2, SD 6.1 | Null mean 70 | Two tailed |
| Before and after training | Paired | Before raw values | After raw values | Right tailed |
| Two independent groups | Welch | n 12, mean 72.4, SD 8.6 | n 10, mean 66.1, SD 7.9 | Two tailed |
Critical T Table
Values below are positive two tailed cutoffs for common alpha levels.
| df | Alpha 0.1 | Alpha 0.05 | Alpha 0.01 |
|---|---|---|---|
| 1 |