Biostatistics and Evidence-Based Literature Appraisal Flashcards

A periodontal RCT reports 20% of control patients and 10% of test patients had recurrent pocket depth ≥5 mm. What is the number needed to treat (NNT)?

Answer: 10

ARR = 20% − 10% = 10%, so NNT = 1/0.10 = 10.

A 95% confidence interval for a mean attachment gain difference is −0.2 to 1.4 mm. What can be concluded at α = 0.05?

Answer: The difference is not statistically significant

The interval includes 0 (no difference), so the result is not statistically significant.

Which test is most appropriate to compare mean probing depth reduction among three independent treatment groups with normally distributed data?

Answer: One-way ANOVA

One-way ANOVA compares means across three or more independent groups.

In a split-mouth design for evaluating a graft material, which analysis is generally appropriate?

Answer: Paired analysis accounting for within-patient correlation

Sites within the same patient are correlated, so paired or mixed-model analysis is needed.

What is the main purpose of intention-to-treat (ITT) analysis?

Answer: To preserve randomization and reduce attrition bias

ITT analyzes participants in the groups to which they were randomized, preserving the balance achieved by randomization.

Which statistic best describes agreement between two examiners' categorical furcation classifications beyond chance?

Answer: Cohen's kappa

Cohen's kappa measures inter-rater agreement corrected for chance.

A Type II error in a clinical trial means:

Answer: Failing to reject a false null hypothesis

A Type II (beta) error is missing a real difference; power equals 1 − beta.