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Biostatistics & Research: INBDE study notes and practice questions

Research and statistics questions ask you to read a short study description and name the design, interpret a result, or spot a source of bias. Evidence-based dentistry is the unifying theme.

276 practice questions · 4 patient cases

Practice Biostatistics & Research

Where it fits in the official INBDE blueprint

Practice and Profession (evaluating scientific literature). Nearest foundation knowledge area: FK 10. See the content outline for the official weights. This mapping is approximate: real items combine a clinical area with a foundation area.

What this area tests

High-yield checklist

Common traps

These notes are original study aids, not official exam content. Confirm clinical details against current guidelines.

Sample questions

1. A chart shows the relationship between vitamin A deficiency and periodontitis, with an odds ratio of 4.1, 95% CI of 1.4-6.4, and p-value < 0.0001. What does this data suggest?

  1. Weak association, statistically significant
  2. Strong association, statistically significant
  3. Strong association, not statistically significant
  4. Weak association, not statistically significant
Show answer and explanation

Correct answer: B. Strong association, statistically significant

Interpretation: (1) Odds ratio of 4.1 — an OR > 1.0 indicates a positive association between vitamin A deficiency and periodontitis; an OR of 4.1 means those with vitamin A deficiency have 4.1 times the odds of periodontitis compared to those without deficiency. An OR of 4.1 is considered a strong association (OR > 3.0 is generally considered strong). (2) 95% CI of 1.4-6.4 — the CI does not include 1.0 (the null value), confirming statistical significance. (3) p < 0.0001 — this extremely small p-value confirms that the result is highly statistically significant. Therefore: strong association, statistically significant.

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2. A forest plot, displaying point estimates and confidence intervals from multiple individual studies on a single graph, is most characteristically used in which type of publication?

  1. A systematic review and meta-analysis
  2. A single case report
  3. A cross-sectional survey
  4. An expert opinion editorial
Show answer and explanation

Correct answer: A. A systematic review and meta-analysis

Forest plots visually combine the effect estimates (with confidence intervals) from multiple individual studies included in a systematic review, along with a pooled summary effect estimate from the meta-analysis — making them the signature visual tool of systematic reviews/meta-analyses.

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3. What type of study is a COHORT study?

  1. Randomized controlled trial
  2. Cross-sectional study
  3. Case-control study
  4. Prospective or retrospective observational study following a group over time
Show answer and explanation

Correct answer: D. Prospective or retrospective observational study following a group over time

A cohort study follows a group (cohort) of people over time, comparing outcomes between exposed and unexposed groups. It can be PROSPECTIVE (forward in time) or RETROSPECTIVE (looking back at records). Cohort studies are observational — no randomization or intervention. They provide strong evidence of causation when prospective.
  • A. Incorrect. A cross-sectional study measures both exposure and outcome at a SINGLE point in time.
  • B. CORRECT. A cohort study follows exposed and unexposed groups over time to compare incidence of outcomes.
  • C. Incorrect. An RCT involves random assignment to intervention or control groups — not observational.
  • D. Incorrect. A case-control study selects participants based on OUTCOME (cases vs. controls) — the reverse of a cohort design.

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4. A study comparing articaine vs lidocaine shows: RR = 3.1, 95% CI = 3.4–4.7, p-value < 0.001. What does this tell us about efficacy?

  1. Articaine is safer to use than lidocaine
  2. Lidocaine is more effective than articaine
  3. Articaine is more effective than lidocaine
  4. Articaine and lidocaine have the same efficacy
Show answer and explanation

Correct answer: C. Articaine is more effective than lidocaine

✓ C) Articaine is more effective than lidocaine is correct.
RR (relative risk/ratio) = 3.1 means articaine's success rate is 3.1× that of lidocaine — indicating superior efficacy. The p-value < 0.001 confirms the result is highly statistically significant (not due to chance). The 95% CI of 3.4–4.7 does not cross 1.0, further confirming significance. Safety is not addressed by these statistics — RR here measures effectiveness, not adverse events.
  • A. RR = 3.1 with CI (3.4-4.7) not crossing 1 and p <0.001 means: articaine achieves the anesthesia outcome 3.1× more often than lidocaine, and this result is STATISTICALLY SIGNIFICANT (p <0.001) and precisely estimated (CI does not cross 1). Therefore, ARTICAINE IS MORE EFFECTIVE THAN LIDOCAINE for anesthetic efficacy.
  • B. RR (Relative Risk) measures EFFICACY, not safety. The RR of 3.1 tells us about how much more likely articaine achieves the outcome than lidocaine — it says nothing about safety.
  • C. If they were equivalent, the RR would be ~1.0 and the CI would include 1. RR of 3.1 with p <0.001 clearly shows they are NOT equivalent.
  • D. RR = 3.1 FAVORS articaine. An RR >1 (when articaine is the reference) means the articaine group has 3.1× MORE of the outcome (presumably, better anesthesia). Lidocaine being more effective is the opposite.

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5. Which of the following study designs is considered an experimental study?

  1. Cross-sectional survey
  2. Case-control study
  3. Cross-sectional study
  4. Randomized clinical trial
Show answer and explanation

Correct answer: D. Randomized clinical trial

Experimental studies involve the investigator actively intervening and assigning participants to groups (experimental vs. control), with randomization to reduce bias. A randomized clinical trial (RCT) is the gold standard experimental study design. Surveys, case-control studies, and cross-sectional studies are all observational (non-experimental) designs — the investigator merely observes without intervention. Cohort studies can be prospective observational studies but are not experimental unless there is an intervention.

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6. When does the prevalence measure of cancer apply to 'cases of cancer in the USA from 2010 until today'?

  1. Incidence
  2. Range
  3. Prevalence
  4. Mean
Show answer and explanation

Correct answer: C. Prevalence

PREVALENCE measures ALL EXISTING CASES of a condition in a population at a given point in time or over a specified period. 'Cases of cancer in the USA from 2010 until today' describes all existing cases over a time period = PERIOD PREVALENCE. INCIDENCE measures only NEW cases occurring in a defined period. Since this includes all cases existing from 2010 to the present (not just new ones), it is prevalence.
  • A. INCORRECT. Incidence measures only NEW cases occurring in a specific time period — it does not count existing cases from previous years.
  • B. INCORRECT. Range describes the spread of data values — not a measure of disease occurrence.
  • C. CORRECT. Period prevalence counts ALL existing cases over a defined time period (2010 to today). This includes cases diagnosed before 2010 that are still present, as well as new cases diagnosed during the period.
  • D. INCORRECT. Mean (average) is a statistical measure of central tendency — not a measure of disease frequency.

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7. Bias in choosing and retaining participants in a study is called:

  1. Sampling bias
  2. Confounding bias
  3. Selection bias
  4. Measurement bias
Show answer and explanation

Correct answer: C. Selection bias

SELECTION BIAS occurs when the participants included in or retained in a study are not representative of the target population — specifically related to HOW participants are selected and retained. Sampling bias is a type of selection bias related to how the sample is drawn. Confounding bias is when a third variable distorts the relationship between exposure and outcome. Measurement/information bias relates to data collection errors. Selection bias is the specific term for participant selection and retention issues. C is correct.

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8. Among randomized controlled trials, cohort studies, and case-control studies, which generally provides the WEAKEST level of evidence due to its retrospective design and susceptibility to recall bias?

  1. Case-control study
  2. Randomized controlled trial
  3. Cohort study
  4. All three provide identical evidence strength
Show answer and explanation

Correct answer: A. Case-control study

Case-control studies, being retrospective and particularly susceptible to recall bias and other forms of bias, are generally considered to provide weaker evidence than cohort studies (which can be prospective) and especially randomized controlled trials (where randomization minimizes confounding and selection bias).

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Patient cases

All Biostatistics & Research questions (276)