Does this conversion result prove an improvement?

No – the data do not prove that Version B is superior.

Why not?

• The two weeks were not randomized; traffic sources (e.g., referral, paid, organic) differed, so any conversion difference could be due to those sources rather than the version.
• The sample size is small (100 visitors per week), so the observed 8 % vs. 14 % difference could be due to random variation.
• External factors (seasonality, day‑of‑week, marketing campaigns) could have changed between the weeks.

Decision recommendation
Run a properly randomized A/B test (or multivariate test) with a larger, balanced sample and control for traffic source. Only then can you statistically assess whether B truly outperforms A.

Uncertainty

• Confounding by traffic source and other time‑varying factors.
• Statistical uncertainty due to the small sample size.
• Potential interaction with other variables (device, location, etc.) that were not controlled.

No, this does not prove B is better. The lack of a randomized split and differing traffic sources introduce confounding variables. Recommendation: Conduct a controlled experiment with random assignment. Uncertainty: Results may be influenced by external factors.

No, this does not prove that Version B is better. The decision recommendation is to not conclude that Version B is better based on this data alone.

Uncertainty:

• No randomized split was used, introducing potential bias.
• Traffic sources differed between the weeks, which could affect conversion rates.
• The sample size is small, making the results less reliable.