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Statistical Significance Calculator: Is Your Difference Real?
Determine if the difference between two results is statistically significant or due to random chance. Essential for A/B testing and comparing survey segments.
How This Calculator Works
The calculator compares two proportions (like conversion rates or survey percentages) to determine if their difference is statistically significant. It calculates the p-value and tells you whether to trust the observed difference.
The Formula
Uses a two-proportion z-test. z = (p1 - p2) / √(p × (1-p) × (1/n1 + 1/n2)) where p is the pooled proportion. The p-value is calculated from the z-score using the normal distribution.
How to Interpret Your Results
A p-value below 0.05 (or your chosen threshold) indicates statistical significance, meaning the difference is unlikely due to chance. A p-value above 0.05 suggests you cannot rule out random variation.
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Frequently Asked Questions
0.05 (95% confidence) is standard. Use 0.01 for important decisions. 0.10 is acceptable for exploratory analysis.
You cannot conclude the difference is real. You may need larger samples, or there may be no true difference. Not significant does not mean equal.
Statistical significance means the difference is real. Practical significance means the difference matters. A 0.1% difference can be statistically significant but practically irrelevant.
Stopping early inflates false positive rates. Use proper sequential testing methods or run to planned sample size.