Quantitative Reasoning Flashcards

A confidence interval for a treatment effect is 1.2 to 3.8 (relative risk). What does this indicate?

Answer: The treatment significantly increases risk — the interval excludes 1

A CI for relative risk that excludes 1.0 indicates statistical significance. Since both bounds are above 1, the treatment is associated with increased risk.

A hospital reduces average length of stay from 6 days to 4.5 days. By what percentage was it reduced?

Answer: 25%

Reduction = 1.5 days. Percentage = (1.5/6) × 100 = 25%.

Two drugs: Drug X reduces systolic BP by 12 mmHg (SD 4), Drug Y by 10 mmHg (SD 8). Which has more consistent effects?

Answer: Drug X — smaller standard deviation relative to effect

Drug X has a smaller SD (4 vs 8) relative to a larger mean reduction, indicating more consistent, predictable effects.

Prevalence of diabetes in UK = 6%. In a GP practice of 2,500 patients, how many are expected to have diabetes?

Answer: 150

Expected = 6% × 2,500 = 0.06 × 2,500 = 150.

A line graph shows weight loss over 12 weeks. Weeks 1–4: steep decline. Weeks 5–8: plateau. Weeks 9–12: gradual decline. At which point is the rate of loss greatest?

Answer: Weeks 1–4

Steepness of slope on a line graph represents rate of change. The steepest section (weeks 1–4) represents the fastest rate of weight loss.

A clinical audit finds: Compliance rate = 73%. Target = 90%. In a sample of 400 procedures, how many must improve to reach the target?

Answer: 68

Current compliant = 73% × 400 = 292. Target = 90% × 400 = 360. Need to improve = 360 − 292 = 68.