CRO Calculator (Conversion Rate) with Statistical Significance
Calculate conversion rate lift and verify A/B test validity. Features Z-score analysis and confidence level estimation for marketing optimization.
Control (A)
Variation (B)
About
Marketing decisions often rely on intuition rather than data, leading to wasted budget on variations that do not statistically outperform the control. This tool isolates the signal from the noise in A/B testing scenarios. By comparing two sample sets - Control (A) and Variation (B) - it calculates the conversion rate probability difference. Accuracy is critical here; a false positive (Type I error) can cause businesses to roll out a losing design, impacting revenue at scale.
The calculator employs the Z-test for two population proportions. It determines if the observed difference is due to the changes made or mere random chance. A confidence level of 95% is the standard threshold for business validity, meaning there is less than a 5% probability that the result is a statistical fluke.
Formulas
The Z-Score is calculated using the pooled sample proportion method:
Where p is the pooled conversion rate:
Reference Data
| Confidence Level | Z-Score Threshold (σ) | Implication |
|---|---|---|
| 90% | 1.645 | Low risk tolerance. Acceptable for minor UI tweaks. |
| 95% | 1.960 | Standard industry benchmark. Solid proof of validity. |
| 99% | 2.576 | High certainty required. Critical infrastructure changes. |
| 99.9% | 3.291 | Near absolute certainty. Medical or financial safety. |
| < 90% | < 1.645 | Not significant. Result indistinguishable from noise. |