Biostatistics Flashcards

A clinical trial reports a 95% confidence interval for the difference in mean blood pressure reduction as (2.1, 8.4 mmHg). Which conclusion is most appropriate?

Answer: We are 95% confident the true difference lies between 2.1 and 8.4 mmHg

A 95% CI means that 95% of such intervals constructed from repeated sampling would contain the true population parameter.

In a study, the Number Needed to Treat (NNT) is calculated as 8. What does this mean?

Answer: 8 patients must be treated for one additional patient to benefit

NNT is the reciprocal of the absolute risk reduction and represents how many patients need treatment for one additional benefit.

Which type of bias occurs when patients who drop out of a clinical trial differ systematically from those who complete it?

Answer: Attrition bias

Attrition bias (also called dropout bias) occurs when loss to follow-up is related to the outcome, distorting results.

A study finds r = 0.85 between drug dose and therapeutic response. What does this Pearson correlation coefficient indicate?

Answer: There is a strong positive linear relationship between dose and response

A Pearson r of 0.85 indicates a strong positive linear association, but does not imply causation.

A researcher increases sample size from 100 to 400. How does this affect the standard error of the mean?

Answer: It is halved

Standard error = SD/√n; quadrupling n doubles √n, so the SE is halved.

In a 2×2 contingency table used for a case-control study, which measure of association is most appropriate?

Answer: Odds ratio

In case-control studies, disease incidence cannot be directly calculated, so the odds ratio is the appropriate measure of association.

A pharmacokinetic study shows a drug's half-life follows a log-normal distribution. What transformation would make it approximately normal?

Answer: Log transformation

A log transformation converts a log-normal distribution to a normal distribution, enabling parametric statistical analyses.