P Value Calculator
Calculate statistical significance from common results reported in medical papers, SPSS, R, Stata, SAS, and thesis outputs.
Required Terms Explained
- Test statistic: the calculated value from your statistical test, such as t, z, chi-square, or F.
- df / degrees of freedom: a number related to sample size and model complexity; it tells the calculator which reference distribution to use.
- Numerator df: the degrees of freedom for the tested effect in an F test, such as group or model df.
- Denominator df: the error or residual degrees of freedom in an F test.
- SE / standard error: the uncertainty around an estimate; smaller SE means a more precise estimate.
- 95% CI: a confidence interval showing the plausible range for the true effect.
- One-tailed vs two-tailed: two-tailed tests look for any difference; one-tailed tests look in one pre-specified direction.
Frequently Asked Questions
What does a p-value below 0.05 mean?
It means the result is conventionally considered statistically significant at the 5% level, assuming the test and study design are appropriate.
Can I use this for SPSS or R output?
Yes. Copy the reported statistic, degrees of freedom, standard error, confidence interval, or sample counts from SPSS, R, Stata, SAS, or a paper.
Should I report exact p-values?
Yes. Report exact p-values whenever possible instead of only writing p < 0.05.