DA0-002 Data Analysis Practice Question
A data analyst runs an A/B test on a new website layout. The test yields a p-value of 0.04 with the null hypothesis being no difference in conversion rates. The significance threshold is α=0.05. Which of the following is the correct conclusion?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Reject the null hypothesis; there is a statistically significant difference in conversion rates.
Since p-value (0.04) < α (0.05), we reject the null hypothesis and conclude there is a statistically significant difference. However, statistical significance does not guarantee practical significance.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The result is not significant; accept the alternative hypothesis.
Why it's wrong here
A p-value of 0.04 falls below α=0.05, so the result is significant and the null is rejected, not accepted. This option is tempting because it correctly identifies the alternative hypothesis as relevant, but it misreads the comparison direction and treats non-rejection as acceptance.
- ✗
Reject the null hypothesis; the new layout is proven to increase conversions.
Why it's wrong here
Rejecting the null is warranted at α=0.05, but a p-value only indicates the result is statistically unlikely under the null; it cannot prove the layout increases conversions or quantify effect size. This option is tempting because rejection is the correct decision, yet it overstates the conclusion by claiming proof of causation.
- ✓
Reject the null hypothesis; there is a statistically significant difference in conversion rates.
Why this is correct
With p = 0.04 falling below the α = 0.05 threshold, the result lies inside the rejection region, so the null hypothesis of no difference is rejected. This satisfies the stem's significance criterion, supporting a statistically significant difference in conversion rates between the layouts.
- ✗
Fail to reject the null hypothesis; there is no evidence of a difference.
Why it's wrong here
With p=0.04 below α=0.05, the null hypothesis is rejected; concluding no evidence of a difference inverts the decision. Failing to reject is tempting because it sounds cautious, and would be correct had p exceeded 0.05, but here the result is statistically significant.
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