A study comparing mean haemoglobin levels between three groups (tribal, rural, and urban children) uses ANOVA. The F-ratio is 8.6 and p=0.001. The ANOVA result tells us:
- A All three group means are significantly different from each other
- B The tribal group mean specifically differs from the urban group mean
- C At least one pair of group means differs significantly, but post-hoc testing is needed to identify which ✓
- D There is no difference between any of the three means
Explanation
One-way ANOVA tests the null hypothesis that all group means are equal. A significant F-ratio (p=0.001) indicates that at least one group mean differs significantly from at least one other, but ANOVA does NOT specify which pair(s) differ. Post-hoc tests (e.g., Tukey's HSD, Bonferroni correction, Scheffe's test) are required to identify the specific pairs of groups that are significantly different, while controlling the familywise error rate for multiple comparisons. Concluding all three groups differ or that any specific pair differs is incorrect without post-hoc testing.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.