Clinical Trial Questions and Answers

Exclusions for Clinical Trials

1. Which of the following individuals is likely to be excluded from a clinical trial?

A) An individual with other diseases besides the disease of interest.

B) An individual whose data is considered to be an outlier. 

C) An individual of who is considered to be a minority.

D) An individual who will have difficulty complying trial protocols.

2. Randomization in a clinical trial is defined as which of the following?

A) The process by which individuals are coupled into groups for comparison in order to minimize bias and confounding.

B) The process by which individuals are assigned a number and are selected through the usage of a pattern which minimizes bias and confounding. 

C) The process by which individuals are randomly assigned to a treatment or control group which minimizes bias and confounding.

D) The process by which individuals are asked to volunteer for a study which minimizes bias and confounding.

3. Assuming 50,000 individuals in the United States are diagnosed every year, and of those individuals diagnosed with HIV each year, approximately 33,500 individuals diagnosed with HIV are gay or bisexual males. What prevalence of the new HIV cases are from members of the population of gay or bisexual males? 

A) 0.67%

B) 6.70%

C) 33.0%

D) 67.0%

4. Ethnicity is best described as which type of variable?

A) Dichotomous variable 

B) Ordinal variable 

C) Categorical variable 

D) Continuous variable

5. A researcher wants to determine the sensitivity of mammograms to determine how effective they are at diagnosing women who have breast cancer. Assume the researcher obtained the above results from a study, calculate and interpret the sensitivity of mammograms for detecting breast cancer.

A) A total of 66.67% of individuals who have breast cancer test positive for breast cancer when using a mammogram as the primary diagnostic test for breast cancer.

B) A total of 68% of individuals who have breast cancer test positive for breast cancer when using a mammogram as the primary diagnostic test for breast cancer.

C) A total of 70.59% of individuals who have breast cancer test positive for breast cancer when using a mammogram as the primary diagnostic test for breast cancer.

D) A total of 92.77% of individuals who have breast cancer test positive for breast cancer when using a mammogram as the primary diagnostic test for breast cancer.

6. A researcher wants to compare the mean concentration of two medications considered biologically equivalent, i.e., two medications that are able to produce the same therapeutic effect at the same level of concentration in the blood. The group of individuals on medication one (n = 32) had a mean blood concentration of 21.7 micrograms per milliliter with a standard deviation of 8.7 micrograms per milliliter. The group of individuals on medication two (n = 32) had a mean blood concentration of 19.4 micrograms per milliliter with a standard deviation of 5.2 micrograms per milliliter. Construct and interpret a 95% confidence interval demonstrating the difference in means for the individuals on medication one when compared to the group of individuals on medication two. 

Randomization in Clinical Trials

A) The researchers are 95% confident that the true mean difference in medication concentration levels between individuals on medication one and individuals on medication two is between 4.867 micrograms per milliliter and 9.467 micrograms per milliliter.

B) The researchers are 95% confident that the true mean difference in medication concentration levels between individuals on medication one and individuals on medication two is between -1.212 micrograms per milliliter and 5.812 micrograms per milliliter.

C) The researchers are 95% confident that the true mean difference in medication concentration levels between individuals on medication one and individuals on medication two is between 11.747 micrograms per milliliter and 16.347 micrograms per milliliter.

D) The researchers are 95% confident that the true mean difference in medication concentration levels between individuals on medication one and individuals on medication two is between 3.477 micrograms per milliliter and 8.077 micrograms per milliliter.

7. A clinical trial is conducted to compare an experimental medication to placebo to reduce the symptoms of asthma. Two hundred participants are enrolled in the study and randomized to receive either the experimental medication or placebo. The primary outcome is self-reported reduction of symptoms. Among 100 participants who receive the experimental medication, 38 report a reduction of symptoms as compared to 21 participants of 100 assigned to placebo. When you test if there is a significant difference in the proportions of participants reporting a reduction of symptoms between the experimental and placebo groups. Use α = 0.05. What should the researcher’s conclusion be for a 5% significance level?  Reject H0 because 2.64 ≥ 1.960. We have statistically significant evidence at α = 0.05 to show that there is a difference in the proportions of patients reporting a reduction in symptoms.

A) We reject H0 at the 5% level because 2.64 is greater than 1.96. We do have statistically significant evidence at α = 0.05 to show that there is a difference in the proportions of patients reporting a reduction in symptoms.

B) We fail to reject H0 at the 5% because -2.64 is less than 1.645. We do not have statistically significant evidence to show that there is a difference in the proportions of patients reporting a reduction in symptoms.

C) We fail to reject H0 at the 5% because -2.64 is less than 1.96. We do have statistically significant evidence at α = 0.05 to show that there is a difference in the proportions of patients reporting a reduction in symptoms.

Types of Variables in Clinical Trials

D) We fail to reject H0 at the 5% because 2.64 is greater than -1.645. We do have statistically significant evidence at α = 0.05 to show that there is a difference in the proportions of patients reporting a reduction in symptoms.

8. A clinical trial is being conducted in order to determine the efficacy of a new drug used to treat Rheumatoid arthritis. The efficacy of the medication will not only be determined by the physical improvement of symptoms but also by using a blood test to examine the concentration C-reactive protein (an inflammatory marker) in an individual’s blood. If the researcher wants a margin of error for the level of C-reactive protein to be less than or equal to 3.0 mg/dL, and if the standard deviation for C-reactive protein concentrations among arthritis patients was previously documented at 8 mg/dL, how many patients should be recruited for each group in the study assuming a 95% confidence interval will be used to quantify the mean differences between the control group and the treatment group?

A) n for the treatment group = 112; n for the control group = 111

B) n for the treatment group = 56; n for the control group = 57

C) n for the treatment group = 55; n for the control group = 55

D) n for the treatment group = 112; n for the control group = 112

9. A researcher notes that there seems to be a difference in the prevalence of high blood pressure among college-educated individuals who consume low amounts of processed foods and the prevalence of individuals who only have a high school education and consume high amounts of processed foods. Use the appropriate hypothesis to test for the independence of the two independent variables presented here at the 5% significance level to ensure confounding has not influenced the study’s results. Then, interpret your response.

A) The chi square value of 37.724 is higher than the chi square value of 3.84; therefore, we do not reject H0 at the 5% level and reject H1, which states that level of education and the amount of processed foods in an individual’s diet are not independent of one another.

B) The chi square value of 37.724 is higher than the chi square value of 3.84; therefore, we do not reject H0 at the 5% level and reject H1, which states that level of education and the incidence of high blood pressure are not independent of one another.

Sensitivity of Mammograms in Clinical Trials

C) The chi square value of 37.724 is higher than the chi square value of 3.84; therefore, we can reject H0 at the 5% level in favor of H1, which states that level of education and the incidence of high blood pressure are not independent of one another.

D) The chi square value of 37.724 is higher than the chi square value of 3.84; therefore, we can reject H0 at the 5% level in favor of H1, which states that level of education and the amount of processed foods in an individual’s diet are not independent of one another.

True/False

10. True or False? Researchers use active-controlled trials to test new medications that are used to treat a particular illness against old medications used to treat the same illness.

11. True or False? Considering the data blow. The mean is 118.44.

100    120   111    115    120   116   125   129   130

12. True or False? A researcher decides to take a random sample of the population and determine the ALT levels of the population, which fall on a continuum. A bar chart would be useful in determining if the ALT levels of the population are normally distributed.

13. True or False? A stratified random sample can be used to ensure underrepresented populations are represented in a study.

14. True or False? Assume a doctor uses a specific form of mesh to repair all hernias in his hernia patients. The makers of the mesh found there was an error that occurred while making the mesh, and the hernia mesh has a 45% chance of failure. The doctor has treated 7 patients with the mesh so far; thus, the probability that the mesh does not fail in all seven patients is .0152. 

15. True or False? It is important for researchers to account for attrition or loss of participants during follow-up.

16. True or False? An r value of .8 indicates a strong positive correlation.

17. True or False? When performing a Mann-Whitney U test, one should always use the higher value of the calculated U values to compare to the critical U value while making the decision rule.  

18. True or False? Considering the data blow. The median is 120.

100    120   111    115    120   116   125   129   130

19. True or False? The margin of error is always greater than or equal to the standard error.

Confidence Intervals in Clinical Trials

20. True or False? If a test is run and p = 0.0356, then we can reject H0 at ? = 0.01.

21. True or False? If a 95% confidence interval for the difference in two independent means is (-4.5 to 2.1), then the point estimate is -2.1.

22. True or False? If a 95% confidence interval for the difference in two independent means is (2.1 to 4.5), there is no significant difference in means.

23. True or False? If a 90% confidence interval for the mean is (75.3 to 80.9), we would reject H0: ?? =70 in favor of H1: ? ≠ 70 at ? = 0.05.

24. True or False? In logistic regression, the predictors are dichotomous, and the outcome is a continuous variable.

25. True or False? The level of significance is the probability that we reject the null hypothesis (in favor of the alternative) when it is actually true.

26. True or False? The level of significance alpha most commonly used are: 0.01, 0.05, 0.1. 

27. True or False? The sample size required to detect an effect size of 0.25 is larger than the sample size required to detect an effect size of 0.50 with 80% power and a 5% level of significance.   

28. The following are body mass index (BMI) scores measured in 12 patients who are free of diabetes and are participating in a study of risk factors for obesity. Body mass index is measured as the ratio of weight in kilograms to height in meters squared. Generate a 95% confidence interval estimate of the true BMI.

25 27 31 33 26 28 38 41 24 32 35 40

29. How many subjects would be needed to ensure that a 95% confidence interval estimate of BMI had a margin of error not exceeding 2 units?

25 27 31 33 26 28 38 41 24 32 35 40

30. Based on the data set below , what is the standard deviation?

25 27 31 33 26 28 38 41 24 32 35 40

31. Peak expiratory flow (PEF) is a measure of a patient’s ability to expel air from the lungs. Patients with asthma or other respiratory conditions often have restricted PEF. The mean PEF for children free of asthma is 306. An investigator wants to test whether children with chronic bronchitis have restricted PEF. A sample of 40 children with chronic bronchitis is studied, and their mean PEF is 279 with a standard deviation of 71. Is there statistical evidence of a lower mean PEF in children with chronic bronchitis? Run the appropriate test at ? = 0.05.  

32.Peak expiratory flow (PEF) is a measure of a patient’s ability to expel air from the lungs. Patients with asthma or other respiratory conditions often have restricted PEF. The mean PEF for children free of asthma is 306. An investigator conducts a study to investigate whether there is a difference in mean PEF in children with chronic bronchitis as compared to those without asthma or other respiratory conditions often have restricted PEF. Data on PEF are collected and summarized below. Based on the data, is there statistical evidence of a lower mean PEF in children with chronic bronchitis as compared to those without? Run the appropriate test at ? = 0.05.  

33. A clinical trial is run to investigate the effectiveness of an experimental drug in reducing preterm delivery to a drug considered standard care and to a placebo. Pregnant women are enrolled and randomly assigned to receive either the experimental drug, the standard drug or a placebo. Women are followed through delivery and classified as delivering preterm (< 37 weeks) or not. The data are shown below.

Is there a statistically significant difference in the proportions of women delivering preterm among the three treatment groups? Run the test at a 5% level of significance.