Measures of Association & Validity

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Questions and Answers

What does an odds ratio (OR) greater than 1 signify in terms of the risk of developing an event?

  • There is no difference in the occurrence of the event between the groups.
  • The event occurs equally in both groups.
  • The event is less likely to occur in the exposed group.
  • The event is more likely to occur in the exposed group. (correct)

In studying the prevalence of periodontal disease, which measure of association is preferred when the outcome is relatively frequent?

  • Prevalence Ratio (PR) (correct)
  • Odds Ratio (OR)
  • Risk Difference (RD)
  • Relative Risk (RR)

Using the formula for odds ratio, what does 'ad / bc' represent?

  • The overall incidence of disease in the population.
  • The ratio of affected to non-affected in both groups. (correct)
  • The ratio of non-exposed and non-affected groups.
  • The proportion of individuals exposed in each group.

What is the implication of the odds ratio being calculated as 5.4 in the context of smokers developing periodontal disease?

<p>The chance of developing the disease is 5.4 times higher in smokers than in non-smokers. (C)</p> Signup and view all the answers

Which study design is typically not associated with calculating an odds ratio?

<p>Randomized Clinical Trial (B)</p> Signup and view all the answers

What is necessary for ensuring internal validity in a study?

<p>Ensuring group comparability (A)</p> Signup and view all the answers

What is the primary concern of validity in a study?

<p>The ability to measure what the study intends to measure (D)</p> Signup and view all the answers

Which factor is primarily related to external validity?

<p>Ability to draw inferences from the sample (C)</p> Signup and view all the answers

Which type of validity addresses the correctness of results for a specific group in a study?

<p>Internal validity (C)</p> Signup and view all the answers

What does external validity primarily assess?

<p>The applicability of results to a larger population (B)</p> Signup and view all the answers

What is one challenge faced by randomized clinical trials in terms of validity?

<p>High internal validity but low external validity (D)</p> Signup and view all the answers

What could threaten the internal validity of a study?

<p>Systematic errors or bias (B)</p> Signup and view all the answers

Why is generalizability important in epidemiological studies?

<p>It allows findings to apply to a broader population. (A)</p> Signup and view all the answers

Which statement about reliability is true?

<p>It involves repeatability of study results under the same parameters. (D)</p> Signup and view all the answers

External validity pertains to which of the following?

<p>The generalizability of study results beyond the sample. (A)</p> Signup and view all the answers

What aspect does external validity take into account when evaluating study findings?

<p>Sample selection criteria and inference possibilities (B)</p> Signup and view all the answers

Which of the following is NOT a component necessary for internal validity?

<p>Random sampling of the population (D)</p> Signup and view all the answers

How can internal validity be improved in a study?

<p>By minimizing systematic errors through careful design (C)</p> Signup and view all the answers

What is a typical limitation of most randomized clinical trials in terms of external validity?

<p>They are mostly conducted in high-income countries (D)</p> Signup and view all the answers

What does a reliable study guarantee?

<p>It will always produce the same results. (D)</p> Signup and view all the answers

In epidemiological studies, internal and external validity should ideally be:

<p>Maximized simultaneously with equal focus (A)</p> Signup and view all the answers

Flashcards

Odds Ratio (OR)

The odds ratio (OR) is a measure of association that quantifies the relationship between an exposure and an outcome. It represents the odds of experiencing the outcome among exposed individuals versus those who are not exposed.

Prevalence Ratio (PR)

The prevalence ratio (PR) measures the association between an exposure and an outcome in a cross-sectional study. It compares the prevalence of the outcome in the exposed group to the prevalence in the unexposed group.

Case-Control Study

A case-control study is a retrospective observational study that investigates the relationship between an exposure and an outcome. It starts with individuals who have the outcome (cases) and those who don't (controls) and looks back to see their exposure status.

Cross-Sectional Study

A cross-sectional study captures data at a single point in time, providing a snapshot of the relationship between an exposure and an outcome. It doesn't follow individuals over time.

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Cohort Study

A cohort study follows a group of individuals (cohort) over time to observe the relationship between an exposure and an outcome. It starts with a group without the outcome and tracks their exposure status over time.

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Internal Validity

The degree to which the results of a study can be confidently attributed to the intervention being studied, without interference from other factors.

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Comparability of Groups

Ensures the groups being compared in a study are similar in all relevant aspects except for the intervention being studied.

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Accuracy in Diagnostic Techniques

The accuracy and reliability of the tools used to measure outcomes in a study.

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External Validity (Generalizability)

The extent to which the results of a study can be generalized to other populations, settings, and times.

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Generalizability

The ability to apply the findings of a study to different groups of people or situations.

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Sample Representativeness

The characteristics of the sample used in a study should be representative of the larger population to which the findings are intended to be generalized.

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Study Design

The design of the study should be appropriate for the research question and the population being studied.

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Limitations of Randomized Clinical Trials

Randomized clinical trials often have strong internal validity but struggle with external validity due to their limited sample demographics.

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Validity

The ability of a study to correctly answer the question it asks. It ensures the results reflect the true relationship between variables.

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Reliability

A study is considered reliable when repeated under similar conditions yields consistent results.

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Bias

A form of systematic error that can threaten internal validity. It occurs when there's a flaw in the study design or execution.

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Internal Validity (in Epidemiology)

Refers to the methodological and statistical aspects of an epidemiological study.

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Study Notes

Measures of Association & Validity

  • Measures of association evaluate the relationship between exposures (risk factors) and outcomes (disease).

  • Validity refers to the accuracy of a study or instrument in measuring what it intends to measure.

  • Reliability is the consistency and repeatability of a study or instrument.

Validity and Reliability

  • A reliable and valid study produces consistent results that accurately measure the intended concept.

  • A valid, but not reliable, study consistently produces accurate data but might not offer the same results if repeated.

  • A reliable, but not valid study returns consistent results but these might not be accurate measures of the intended concept.

Dimensions of Validity

  • Internal validity assesses whether the observed relationship within the study truly exists. It ensures the observed effect is due to variables within the study, not extraneous factors.

  • External validity assesses the generalizability of the study's results to a larger population beyond the study sample.

Reliability

  • Reliable studies must produce similar results when repeated under identical conditions.

Validity

  • Valid studies correctly address the question they aim to answer, measuring what they intend to measure.

  • A study is valid if results reflect the truth, meaning limited systematic and random error.

  • Epidemiological studies ideally should have both internal and external validity.

Internal Validity

  • A study's internal validity is paramount; if the study is not internally valid, it cannot be of any use.

  • Internal validity refers to the confidence that the study's findings are genuine and not due to confounding variables.

  • Threats to internal validity include biases and systematic errors that can affect the relationships observed in the study.

  • Ensuring the comparability of groups and accuracy of measurement tools maintains internal validity.

External Validity

  • External validity concerns the generalizability of findings to other populations and settings beyond the study's specific context.

  • External validity allows conclusions from a study to be applicable in different settings and groups of people similar to the ones in the study.

  • Ensuring comparable groups and the appropriate measurement tools strengthens external validity.

Measures of Association

  • Epidemiological studies often aim to evaluate the association between exposures and outcomes.

  • Contingency tables are instrumental in calculating association measures.

Types of epidemiological studies, measures of association

  • Randomized clinical trials (RCTs): Use of prevalence ratio.

  • Cohort studies: Use relative risk.

  • Case-control studies: Use of odds ratio.

  • Cross-sectional studies: Use of prevalence ratio or odds ratio (where prevalence is high).

Calculation of measures in experimental studies

  • Calculation of relative risk (RR), absolute risk reduction (ARR), and number needed to treat (NNT) are essential aspects of interpreting experimental studies.

  • These measures aid in understanding the impact and effectiveness of an intervention.

Types of studies and their measure applications

  • Cohort studies use relative risk (RR) calculations
  • Case-control studies use odds ratio (OR) calculations.
  • Cross-sectional studies use prevalence ratio (PR) calculations, or an odds ratio depending on the prevalence of the outcome.

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