Chapter·BiostatisticsP-values and confidence intervals

Effect sizes and confidence intervalsDownloads

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1

Group of 100 medical students took an end of the year exam. The mean score on the exam was 70%, with a standard deviation of 25%. The professor states that a student's score must be within the 95% confidence interval of the mean to pass the exam. Which of the following is the minimum score a student can have to pass the exam?

A45%

B63.75%

C67.5%

D20%

E65%

2

You are conducting a study comparing the efficacy of two different statin medications. Two groups are placed on different statin medications, statin A and statin B. Baseline LDL levels are drawn for each group and are subsequently measured every 3 months for 1 year. Average baseline LDL levels for each group were identical. The group receiving statin A exhibited an 11 mg/dL greater reduction in LDL in comparison to the statin B group. Your statistical analysis reports a p-value of 0.052. Which of the following best describes the meaning of this p-value?

AThere is a 95% chance that the difference in reduction of LDL observed reflects a real difference between the two groups

BThough A is more effective than B, there is a 5% chance the difference in reduction of LDL between the two groups is due to chance

CIf 100 permutations of this experiment were conducted, 5 of them would show similar results to those described above

DThis is a statistically significant result

EThere is a 5.2% chance of observing a difference in reduction of LDL of 11 mg/dL or greater even if the two medications have identical effects

3

An investigator is studying the effect of antihypertensive drugs on cardiac output and renal blood flow. For comparison, a healthy volunteer is given a placebo and a continuous infusion of para-aminohippuric acid (PAH) to achieve a plasma concentration of 0.02 mg/ml. His urinary flow rate is 1.5 ml/min and the urinary concentration of PAH is measured to be 8 mg/ml. His hematocrit is 50%. Which of the following values best estimates cardiac output in this volunteer?

A8 L/min

B3 L/min

C4 L/min

D1.2 L/min

E6 L/min

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