- Which of the following is correct regarding measures of variability?
(A) Range can be both descriptive and inferential.
(B) Standard error of the mean (SEM) is always larger than SD.
(C) All values contained in a confi dence interval (CI) are statistically possible.
(D) CI is a descriptive measure only.
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Answer C is correct because all values within a CI are statistically possible. Answer A is incorrect because range is descriptive only. Range is not inferential because one
is unable to “infer” statistical signifi cance for a data set based on range. Answer B is incorrect because SEM is always smaller than SD. Answer D is incorrect because CI
is not only descriptive but also inferential since one is able to “infer” statistical significance for a data set based on CI.
- A study was performed to determine the effect of a new antipsychotic agent (Drug A) on psychosis in patients with underlying schizophrenia as compared to placebo. A sample size of 300 patients was calculated to be needed based on an of 0.05 and a of 0.2. The double-blind, parallel, superiority trial was performed in 350 patients for 8 weeks. At the end of the 8-week period, the new antipsychotic agent was found to induce remission in 20% of patients as compared to 19% in the placebo group (P 0.04).Which of the following statements is true based on the results of the study?
(A) Drug A was found to have a statistically significant and clinically significant difference on remission of psychosis as compared to placebo.
(B) Drug A was found to have a statistically significant difference but not a clinically significant difference on remission of psychosis as compared to placebo.
(C) Drug A was found to have a clinically significant difference but not a statistically significant difference on remission of psychosis as compared to placebo.
(D) Drug A was not found to have a clinically or statistically significant difference on remission of psychosis as compared to placebo.
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Answer B is correct. The difference was statistically significant because the P value was .04. Based on this Pvalue, there is a 4% chance that a type 1 error occurred,which is less than the prespecifi ed acceptable risk of 5% (preset was 0.05 or 5%). However, the diff erence was not clinically meaningful because there was only a 1% difference in the primary end point (induction of remission) between the treatment groups. For these reasons, answers A, C, and D are incorrect.
(For the next two questions) A study of the effects of bupropion (Zyban) versus nicotine gum (Nicorette) on the primary end point of change in the number of cigarettes smoked per day in a parallel, randomized trial. The investigators plan to include 450 subjects (150 in each arm) to reach statistical significance based on a of 0.2 and of 0.05.
**Which of the following statistical tests would be the most appropriate? (assume no confounders)
(A) One-way ANOVA
(B) Chi-square
(C) Fisher exact test
(D) Friedman test
(E) t test
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Answer E is correct because a t test is the test of choice for evaluating statistical differences in parametric data (change in the number of cigarettes smoked daily) when only two groups are being evaluated and there are no detected confounders. Answer A is incorrect because one-way ANOVA is used for testing three or more groups. Answers B and C are incorrect because chi-square and Fisher exact test are used to test nominal data. Answer D is incorrect because Friedman test is used to test ordinal data.
**Which of the following statistical tests would be the most appropriate if the study had evaluated three groups instead of only two? (i.e., bupropion [Zyban]vs. nicotine patches [Nicoderm CQ] vs. nicotine gum[Nicorette])
(A) One-way ANOVA
(B) Chi-square
(C) Fisher exact test
(D) Friedman test
(E) Student’s t test
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Answer A is correct because one-way ANOVA is used to test parametric data (change in the number of cigarettes smoked daily) when there are three independent
groups and no detected confounders are present. Answers B and C are incorrect because chi-square and Fisher exact test are used to test nominal data. AnswerD is incorrect because Friedman test is used to test ordinal data. Answer E is incorrect because t test is used for evaluating statistical differences in parametric data
when only two groups are being evaluated.
- A study is designed to evaluate the change in blood pressure lowering between metoprolol tartrate (Lopressor®) and metoprolol succinate (Toprol XL®).The investigators decide to perform a parallel trial in 200 patients. There were significant baseline differences between the groups in diet and exercise.
Which of the following statistical tests would be most appropriate?
(A) One-way ANOVA
(B) Chi-square
(C) Fisher exact test
(D) ANCOVA
(E) Student’s t test
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Answer D is correct because ANCOVA is used to test parametric data (change in BP) when two or more groups are being evaluated and two or more confounders (diet and exercise diff erences) are detected. Answer A is incorrect because one-way ANOVA is used
when no detected confounders are present. Answers B and C are incorrect because chi-square and Fisher exact test are used to test nominal data. Answer E is incorrect because t test is used when no detected confounders are present.
- The makers of eplerenone (Inspra) want to design a study to compare their medication to the current standard of spironolactone (Aldactone) in the treatment of heart failure. Th ey decide to perform a parallel trial of the two agents in 2000 patients with NYHA classes II to IV heart failure over 2 years. The primary end point is mortality. Which of the following statistical tests would be most appropriate to use?
(A) ANOVA
(B) Fisher exact test
(C) Chi-square
(D) Mann-Whitney U test
(E) Student’s t test
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- A retrospective study produces correlation/regression analysis between a high sodium intake (2.4 g/day) and hypertension (HTN) reporting an r 0.45.
Which of the following is correct?
(A) 20% of HTN may be explained by high sodium intake.
(B) 20% of HTN is not explained by high sodium intake.
(C) 80% of HTN is explained by high sodium intake.
(D) 55% of HTN is not explained by high sodium intake.
(E) 45% of HTN may be explained by high sodium intake.
- A study was performed to evaluate a possible between the use of the herbal product Goldenseal and changes in pain relief (based on pain scale scores).
Which type of correlation analysis should be used in this trial?
(A) Pearson
(B) Spearman
(C) Linear
(D) Cox
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- (For the next two questions) In the RELY trial, dabigatran (Pradaxa) was compared with warfarin (Coumadin) for the prevention of cerebrovascular accident (CVA) in atrial fibrillation (AF) patients. The primary outcome in this trial was CVA or systemic thromboembolism (TE). The results are presented as follows:
What can be concluded about the outcome “CVA or TE”?
(A) Dabigatran (Pradaxa) has a clinically significant lower risk than warfarin (Coumadin), although it is not statistically significant because the CI does not include 1.
(B) Dabigatran (Pradaxa) has a clinically signifi cant lower risk than warfarin (Coumadin), although it is not statistically signifi cant because the CI does not include 0.
(C) Dabigatran (Pradaxa) has a clinically significant higher risk than warfarin (Coumadin), and it is statistically signifi cant because the CI does not include 0.
(D) Dabigatran (Pradaxa) has a clinically significant lower risk than warfarin (Coumadin), and it is statistically signifi cant because the CI does not include 1.
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What can be concluded about the outcome “MI”?
(A) Dabigatran (Pradaxa) has a higher MI risk than warfarin (Coumadin), although it is not statistically significant because the CI includes 1.
(B) Dabigatran (Pradaxa) has a higher MI risk than warfarin (Coumadin), although it is not statistically signifi cant because the CI does not include 0.
(C) Dabigatran (Pradaxa) has a higher MI risk than warfarin (Coumadin), and it is statistically significant because the CI includes 1.
(D) Dabigatran (Pradaxa) has a higher MI risk than warfarin (Coumadin), and it is statistically significant because the CI does not include 0.
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- A researcher was interested in examining the association between postmenopausal hormone replacement therapy (HRT) and development of heart disease. All women who were characterized as postmenopausal were approached regarding their interest in participating in the study by answering a questionnaire annually regarding their medication use and medical conditions. Of the 16,168 women who provided consent, the average length of follow-up was 12.5 years (range, 6 to 16 years). Which of the following best describes the study design?
(A) Case-control study
(B) Prospective cohort study
(C) Randomized controlled trial
(D) Meta-analysis
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- An investigator wishes to study a new drug for the treatment of hypertension in patients with diabetes. What is the best type of trial design the investigator should use for determining causality in this particular study?
(A) A case-control study
(B) A prospective cohort study
(C) A prospective, randomized, placebo-controlled trial
(D) A prospective, randomized, standard-of-care comparison trial
(E) A meta-analysis
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Which of the following would be appropriate for a crossover design study?
(A)Effects of Drug A versus Drug B on hypertension in 100 patients
(B)Effects of varenicline (Chantix) compared to placebo on smoking cessation
(C)Effects of fluticasone/salmeterol (Advair) and budesonide/formoterol (Symbicort) on asthma exacerbations
(D)Effects of hydralazine and hydrochlorothiazide (Microzide) on all-cause mortality
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