Chapter·BiostatisticsOdds ratio vs. relative risk

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1

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

2

A medical research study is evaluating an investigational novel drug (medication 1) as compared with standard therapy (medication 2) in patients presenting to the emergency department with myocardial infarction (MI). The study enrolled a total of 3,000 subjects, 1,500 in each study arm. Follow-up was conducted at 45 days post-MI. The following are the results of the trial: Endpoints Medication 1 Medication 2 P-Value Primary: death from cardiac causes 134 210 0.03 Secondary: hyperkalemia 57 70 0.4 What is the relative risk of death from a cardiac cause, expressed as a percentage? (Round to the nearest whole number.)

A64%

B42%

C72%

D36%

E57%

3

A researcher is trying to determine whether a newly discovered substance X can be useful in promoting wound healing after surgery. She conducts this study by enrolling the next 100 patients that will be undergoing this surgery and separating them into 2 groups. She decides which patient will be in which group by using a random number generator. Subsequently, she prepares 1 set of syringes with the novel substance X and 1 set of syringes with a saline control. Both of these sets of syringes are unlabeled and the substances inside cannot be distinguished. She gives the surgeon performing the surgery 1 of the syringes and does not inform him nor the patient which syringe was used. After the study is complete, she analyzes all the data that was collected and performs statistical analysis. This study most likely provides which level of evidence for use of substance X?

ALevel 3

BLevel 1

CLevel 4

DLevel 5

ELevel 2

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