How to use: Calculate statistical significance in hypothesis testing. Enter Test Statistic (calculated value from your statistical test) and Degrees of Freedom (typically sample size minus 1 or 2 depending on test). Results show p-value (probability of obtaining results by chance). Interpretation: p < 0.05 = statistically significant (reject null hypothesis), p > 0.05 = not significant (cannot reject null). Lower p-value = stronger evidence against null hypothesis. Thresholds: p<0.01 highly significant, p<0.05 significant, p<0.10 marginally significant. Applications: clinical trials (drug effectiveness), A/B testing (website changes), scientific research (experimental validation), quality control. Critical for research validity and data-driven decisions.