MCAT Math Practice Test 2: Reasoning About the Design and Execution of Research

1. An experimenter is attempting to investigate the effect of a new antibiotic on E. coli. He plates cells and administers one milliliter of the antibiotic. Which of the following is an appropriate negative control in this experiment?

• A. A plate with no cells that was coated with one milliliter of antibiotic.
• B. A plate with E. coli and no additional treatment.
• C. A plate with E. coli and one milliliter of isotonic saline.
• D. A plate of epithelial cells treated with one milliliter of antibiotic.

2. Which of the following would best establish a causal link?

• A. A cross-sectional study using survey data for hand-washing and colds.
• B. A case–control study of an exposure during childhood and development of a certain disease later in life.
• C. A randomized clinical controlled trial of a new antipyretic drug.
• D. An IQ test where the results are later segregated by gender.

3. An experimenter is attempting to determine the internal energy of a well-known compound He cleans his glassware, completes the synthesis, calibrates a bomb calorimeter, and then uses it to measure the appropriate thermodynamic values. Which of the following errors did he make?

• A. He did not determine if the compound was novel or if the information has already been determined.
• B. He did not have a specific goal at the beginning of his research.
• C. He should not be involved in both the synthesis of the compound and later testing.
• D. He should have calibrated the calorimeter before the synthesis of the compound.

4. A researcher wishes to generate a parameter for American women's mean weight. Which of the following is the most significant concern?

• A. Measuring a person's weight may have psychological consequences and is unethical.
• B. Gathering all of the necessary study participants would be prohibitive.
• C. Knowing the average weight of women does not provide any useful information.
• D. Enough studies have already been conducted on this topic to render it unnecessary.

5. A cross-sectional study in which current smoking status and cancer history are assessed simultaneously cannot satisfy which of Hill's criteria?

• A. Strength
• B. Coherence
• C. Plausibility
• D. Temporality

6. After randomization, it is discovered that one group in a study has almost twice as many women as the other. Which of the following is an appropriate response?

• A. Move men and women between groups manually so that they have the same gender profile.
• B. Check the randomization algorithm; if it is fair, continue with the research.
• C. Eliminate all of these subjects because of potential bias and randomize a new cohort.
• D. Keep the current cohort and continue randomizing subjects until the gender profiles are equal.

7. An experimenter is attempting to determine the effects of smoking on very low birth weight (VLBW) and of VLBW on IQ. Which of the following statements is correct?

Smoking is an independent variable.

Smoking is a dependent variable.

VLBW is an independent variable.

VLBW is a dependent variable.

• A. I only
• B. II and IV only
• C. I, III, and IV only
• D. II, III, and IV only

8. A study is performed on a new medication. Subjects in the experimental group are told about the potential side effects of the medication, while subjects in the placebo group are not. The subjects have no contact with each other and do not know in which group they are placed. The side effects end up being significantly more severe in the treatment group, when seen by the same assessor physician. This is most likely caused by which of the following?

• A. Physician unblinding only
• B. Patient unblinding only
• C. Both physician and patient unblinding
• D. Both physician and patient blinding

9. Which of the following relationships between measurement error and overall error is correct?

• A. Unreliable data leads to confounding.
• B. Invalid data leads to confounding.
• C. Unreliable data leads to bias.
• D. Invalid data leads to bias.

10. A new study of a weight loss drug uses a radio advertisement to generate study participation. What type of error is most likely to result?

• A. Hawthorne effect
• B. Selection bias
• C. Confounding
• D. Detection bias

11. A researcher designing a study has paid for it to be professionally translated into several languages. She discusses the potential risks and benefits with each participant and allows them to bring documentation home for review before committing to the study. This researcher has put special focus on:

• A. justice by explaining potential unnecessary risks.
• B. beneficence by describing the potential benefits of the study.
• C. respect for persons by acknowledging the subject's perspective and rights.
• D. selection bias, by making the recruitment documents inclusive.

12. Which of the following methods would be most appropriate for an initial assessment of hemoglobin saturation during an experiment about breath holding?

• A. A pulse oximeter, which uses a small light on an adhesive bandage.
• B. An arterial cannula, which permits repeated blood draws with a single puncture.
• C. Repeated venipuncture, because a single puncture would cause data overlap.
• D. A Swan–Ganz catheter inserted through the femoral artery, which can measure saturation nearest the heart.

13. A medical student attempting to impress her attending physician refers to a recent article that says that there is a statistically significant difference in pregnancy length with a new therapy. Which of the following is most likely to be a valid criticism of the article?

• A. Medical students usually reference articles in the newest journals, which may be unreliable.
• B. The effect didn't change patient outcomes, only a secondary measure.
• C. There is a lack of internal validity in the results, despite significance.
• D. Selection bias is inherent in the scientific process.

14. Which sample would be the most appropriate participants for a study on hormone replacement therapy for postmenopausal symptoms?

• A. Prepubescent girls
• B. Premenopausal adult women
• C. Pregnant women
• D. Postmenopausal women

15. Use of a colorimetric assay to determine protein concentration may be subject to all of the following EXCEPT:

• A. the use of standards.
• B. measurement error.
• C. the Hawthorne effect.
• D. systematic error.