RD Exam Practice Test

RD Exam Research Applications Practice Questions

Research Applications makes up 3 of every 50 questions on a Tigertest RD Exam practice test. Here are 10 of the 12 questions on it, each with the answer and the reason.

Updated 2026-11-10 by the Tigertest team. Based on the CDR Registration Examination for Dietitians test specifications. Original questions; 50 per test, weighted like the real exam. Not affiliated with the Commission on Dietetic Registration.

1. 1. Which study design best shows that a nutrition intervention causes an outcome?

   • A.Cross-sectional survey
   • B.Randomized controlled trial
   • C.Prospective cohort study
   • D.Case-control study

   Answer: B. Random assignment balances known and unknown confounders between groups, so a difference in outcome can be attributed to the intervention. Observational designs show association only.

2. 2. Researchers compare past diets of people with colon cancer and matched people without it. What design is this?

   • A.Clinical trial
   • B.Ecological study
   • C.Cohort study
   • D.Case-control study

   Answer: D. A case-control study starts from the outcome and looks back at exposures. It reports an odds ratio; a cohort study follows exposed and unexposed people forward and reports relative risk.

3. 3. A study concludes a supplement lowers LDL when, in fact, it has no effect. What error is this?

   • A.Type I error
   • B.Recall bias
   • C.Type II error
   • D.Sampling bias

   Answer: A. A Type I error rejects a true null hypothesis (a false positive); its chance is the alpha level, often 0.05. A Type II error misses a real effect, often because the sample is too small.

4. 4. A screening tool flags 72 of the 80 malnourished patients in a sample. What is its sensitivity?

   • A.80%
   • B.10%
   • C.90%
   • D.72%

   Answer: C. Sensitivity is true positives / all who have the condition: 72 / 80 = 0.90. The 8 missed are false negatives, which is 10% of the malnourished patients.

5. 5. Before a study enrolls hospital patients, which body must review it to protect participants?

   • A.Joint Commission surveyors
   • B.Hospital billing office
   • C.Institutional Review Board
   • D.Food and Drug Administration

   Answer: C. An IRB reviews research with human subjects for risks, informed consent and privacy before it begins. The FDA becomes involved only for certain drug, device or food additive studies.

6. 6. In a study of sodium intake and blood pressure, which is the dependent variable?

   • A.Blood pressure
   • B.Age of subjects
   • C.Study location
   • D.Sodium intake

   Answer: A. The dependent variable is the outcome measured; the independent variable (sodium intake) is the one changed or compared. Age is a possible confounder to control for.

7. 7. A set of daily intakes is strongly skewed by a few very high values. Which measure best describes the typical intake?

   • A.Standard deviation
   • B.Mean
   • C.Range
   • D.Median

   Answer: D. The median is the middle value and is not pulled by outliers, so it suits skewed data. The mean is pulled toward the extreme values, and range and SD describe spread, not the center.

8. 8. A scale gives the same weight each time a patient steps on it, but it reads 2 kg too high. How would you describe it?

   • A.Neither valid nor reliable
   • B.Reliable but not valid
   • C.Valid but not reliable
   • D.Both valid and reliable

   Answer: B. Reliability is consistency; validity is accuracy. A scale that repeats the same wrong value is reliable but biased, so its readings are not valid until it is recalibrated.

9. 9. Which statistical test compares mean weight loss across three diet groups?

   • A.Pearson correlation
   • B.Analysis of variance
   • C.Chi-square test
   • D.Paired t-test

   Answer: B. ANOVA compares means of three or more groups. A t-test compares two means, chi-square compares counts in categories, and correlation measures how two continuous variables move together.

10. 10. A study finds r = 0.85 between fruit intake and serum vitamin C. What can be concluded?

    • A.A weak negative association
    • B.No relationship at all
    • C.Fruit intake causes the level
    • D.A strong positive association

    Answer: D. An r near +1 shows a strong positive linear association, but correlation alone does not prove cause. A negative r would mean one rises as the other falls.