Chapter 8 

Multiple Choice

1. A researcher is conducting a study to determine the mean trough dosage of medication for a population. Assuming a previous study was conducted for the same medication and the mean trough dose was found to be 490 mg with a standard deviation of 40 mg, calculate the margin of error for a 95% confidence interval assuming the previous study enrolled 350 individuals.

A) E = ± 4.19

B) E = ± 3.52

C) E = ± 0.22

D) E = ± 78.40

2. A researcher is conducting a study to determine the mean trough dosage of medication for a population. Assume a previous study was conducted for the same medication and the mean trough dose was found to be 490 mg with a standard deviation of 40 mg. If the researcher wants to be 95% confident the true mean trough dosage of the medication is within 10 mg of the true mean trough dosage, what sample size is needed?

A) n = 7

B) n = 8

C) n = 44

D) n = 62

3. A researcher is conducting a study to determine the mean trough dosage of medication for a population. Assume a previous study was conducted for the same medication and the mean trough dose was found to be 490 mg with a standard deviation of 40 mg. If the researcher wants to be 95% confident the true mean trough dosage of the medication is within 10 mg of the true mean trough dosage, what sample size is needed if the study is predicted to have an 88% retention rate?

A) n = 8

B) n = 50

C) n = 55

D) n = 71

4. A researcher wants to calculate the prevalence of Alzheimer’s among members of a specific community who are 65 years of age and older. The researcher needs to know how many individuals who are 65 years of age or older need to be recruited for the study to ensure the estimated prevalence will be within 1.0% of the true proportion. Calculate the sample size needed by the researcher if a national study has shown 11.11% of individuals 65 years of age have Alzheimer’s and the researcher wants to be 95% confident of the estimate.

A) n = 3,794

B) n = 2,673

C) n = 6,549

D) n = 152

5. A clinical trial is being conducted in order to determine the efficacy of a new drug that will be used to treat rheumatoid arthritis. The efficacy of the medication will not only be determined by the physical improvement of symptoms but will also be determined by using a blood test to examine the concentration of 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 2.0 mg/d and if the standard deviation for C-reactive protein concentrations among arthritis patients was previously documented at 7 mg/dL, how many patients should be recruited for each group of individuals 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 = 95 and n for the control group = 95

B) n for the treatment group = 48 and n for the control group = 48

C) n for the treatment group = 47 and n for the control group = 48

D) n for the treatment group = 48 and n for the control group = 47

True/False

1. True or False? To calculate the finalized n for a study, one should take the total number of participants needed to ensure the desired confidence interval and divide it by the proportion of individuals expected to be retained throughout the course of the study.

2. True or False? A researcher wants to be sure the mean difference in the change in blood pressure has a margin of error no more than 5 points and the difference in the standard deviation between the mean blood pressure points from the first medication used to treat high blood pressure and the second medication used to treat high blood pressure is 14 points. The desired sample size required to ensure a 95% confidence interval for the proposed study used to compare the efficacy of two medications used to treat high blood pressure during a cross-over trial is n = 31.

3. True or False? A researcher wants to estimate the impact prenatal care during pregnancy can have on premature deliveries by conducting a retrospective case-control study on new moms. If the prevalence of premature births is approximately 10.9%, the researcher should enroll a total of 586 women in the study if the researcher wants to construct a 90% confidence interval for the difference in proportions that has a margin of error of no more than 3%.

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

5. True or False? The effect size is the difference in the parameter of interest that represents a clinically meaningful difference (in standard deviation units).

Chapter 9

Multiple Choice

1. A specific medication used to prevent strokes, heart attacks, and blood clots requires a different dosage of medication for members of the African American population than the Caucasian population because a specific gene affects the way the drug is metabolized within the body. This is an example of which of the following?

A) Confounding 

B) Effect modification

C) Selection bias 

D) Differential bias

2. A new and relatively expensive medication is released into the population to treat type II diabetes. A doctor notices that poor patients are less likely to see effects from the medication than more wealthy patients, but after conducting a survey the doctor finds the poor patients are less likely to fully comply with their medication regimen because they cannot afford to take the medication on a regular basis. This is an example of which of the following?

A) Confounding

B) Statistical interaction

C) Selection bias

D) Recall bias

3. Research has found that circumcision has a protective effect and helps prevent HIV in men who have sex with women, but circumcision does not seem to have the same protective effect helping to prevent HIV in men who have sex with men. This is an example of which of the following?

A) Confounding

B) Effect modification

C) Selection bias

D) Recall bias

4. A researcher notes that there seems to be a difference in the prevalence of high cholesterol among individuals who smoke and consume diets high in processed food and the prevalence of high cholesterol among individuals who do not smoke and do not consume diets high in processed foods. Use the appropriate hypothesis to determine if diet and smoking status are related (independent) at the 5%.  This is the first step in determining if confounding has influenced the study’s results. Then interpret your response.

A) The chi square value of 4.65 is higher than the chi square value of 3.84, therefore we can accept H0 at the 5% level and reject H1, which states that smoking status and the amount of processed foods in an individual’s diet are not independent of one another.

B) The chi square value of 4.65 is higher than the chi square value of 3.84, therefore we can accept H0 at the 5% level and reject H1, which states that smoking status and the incidence of high cholesterol are not independent of one another

C) The chi square value of 4.65 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 smoking status and the incidence of high cholesterol are not independent of one another.

D) The chi square value of 4.65 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 smoking status and the amount of processed foods in an individual’s diet are not independent of one another. 

5. A researcher notes that there seems to be a difference in the prevalence of individuals who are medication adherent and have high levels of education along with a high health literacy and the prevalence of individuals who are not medication adherent and have low levels of education along with a low health literacy. Use the appropriate hypothesis to determine if education level and health literacy status are related (independent) at the 5%.  This is the first step in determining if confounding has influenced the study’s results.  Then interpret your response.

A) The chi square value of 0 is lower than the chi square value of 3.84, therefore we can reject H0 in favor of H1, which states that an individual’s level of education and medication adherence status are not independent of one another.

B) The chi square value of 0 is lower than the chi square value of 3.84, therefore we can accept H0 and reject H1, which states that an individual’s level of health literacy and medication adherence status are not independent of one another.

C) The chi square value of 0 is lower than the chi square value of 3.84, therefore we can accept H0 and reject H1, which states that an individual’s level of education and level of health literacy status are not independent of one another.

D) The chi square value of 0 is lower than the chi square value of 3.84, therefore we can accept H0 in reject H1, which states that an individual’s level of education and health literacy status are independent of one another.

True/False

1. True or False? An r value of –0.3 indicates a weak negative association.

2. True or False? An r value of 0.5 indicates a positive moderate correlation.

3. True or False? A linear regression equation and multiple linear regression equations can be used to calculate y if one is given the x values. However, a logistic regression equation cannot be used to calculate y when one is given x value.

4. True or False? Multiple logistic regression analysis applies when there is a single dichotomous outcome and more than one independent variable.

5. True or False? Multivariable methods include a number of specific procedures to simultaneously assess the relationships between several exposure or risk factor variables and a single outcome.