Confidence intervals that include zero
The 95% confidence interval for the difference in mean scores between two groups is −2 to 6 points. What can be concluded?
Answer D: explanation for every choice
A
Significance at α = 0.05 would require a 95% interval that excludes 0.
B
The interval describes the uncertainty in the mean difference, not the spread of individual scores.
C
2 is the point estimate (the midpoint). The interval reflects uncertainty around it.
D
Correct. The interval includes 0, so a true difference of zero is consistent with the data at this level.
TakeawayA 95% CI for a difference that includes 0 → not significant at 0.05.
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Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID ps154.