PBH 452: Epidemiology - Estimating Risk & Study Associations

Vocabulary practice flashcards covering Chapter 12: Estimating Risk, measures of association (Odds Ratio and Relative Risk), study design types, and common forms of bias in epidemiology.

Double Blinding

A study blinding technique in which both the researchers and the participants are unaware of which group the participants have been assigned to.

Selection Bias

A systematic error resulting from how study participants are recruited or selected, such as recruiting participants exclusively from a single hospital like New Hanover Regional Medical Center.

Information Bias

A systematic measurement error or misclassification in the collection of participant data, such as participant weights being recorded off by 2 pounds due to an improperly calibrated scale.

Confounding Bias

A distortion of an association between an exposure and an outcome caused by an unconsidered third variable, such as failing to account for pre-existing health conditions when assessing the relationship between walking minutes and mental well-being.

Placebo Effect

A phenomenon where a participant allocated to a control group exhibits real or perceived symptom relief after receiving an inert treatment, such as a sugar pill.

Cross-over RCT

A randomized controlled trial design where participants in the intervention group during the first phase switch to the control group during the second phase after completing a washout period.

Study Design Hierarchy (Validity and Cost)

The progressive ranking of epidemiological study designs showing that validity and cost increase from case report/case series, to ecologic, cross-sectional, case-control, cohort, randomized controlled trial, and systematic review or meta-analysis.

Variable

Any quantity that can have different values across individuals or study units.

Positive Association

A relationship between two variables where an increase in the value of one variable is accompanied by an increase in the value of the other variable.

Negative (Inverse) Association

A relationship between two variables where an increase in the value of one variable is accompanied by a decrease in the value of the other variable.

Standard 2x2 Contingency Table

A matrix used to categorize subjects by exposure status ($E+$ and $E-$) and disease status ($D+$ and $D-$), with cells defined as $a$ (exposed and diseased), $b$ (exposed and healthy), $c$ (unexposed and diseased), and $d$ (unexposed and healthy).

Odds Ratio (OR)

A measure of association used in case-control studies that compares the odds of exposure among cases to the odds of exposure among controls, calculated as $\frac{a \times d}{b \times c}$.

Odds Ratio Greater Than 1 ($OR > 1$)

Indicates a positive association where the odds of exposure among cases is greater than the odds of exposure among controls.

Odds Ratio Less Than 1 ($OR < 1$)

Indicates an inverse or protective association where the odds of exposure among cases is lower than the odds of exposure among controls.

Odds Ratio Equal to 1 ($OR = 1$)

Indicates that the odds of exposure among cases is identical to that among controls, demonstrating no association between exposure and disease.

Relative Risk (RR)

A measure of association in cohort studies and clinical trials calculated as the ratio of disease incidence in the exposed group to disease incidence in the unexposed group: $\frac{a / (a + b)}{c / (c + d)}$.

Relative Risk Greater Than 1 ($RR > 1$)

Indicates a positive association demonstrating that the exposure variable is a risk factor for the disease.

Relative Risk Less Than 1 ($RR < 1$)

Indicates a negative (inverse) association demonstrating that the exposure variable is protective against the disease.

Relative Risk Equal to 1 ($RR = 1.00$)

Indicates that the risk of disease in the exposed group is identical to the risk in the unexposed group, signifying no association.

Cross-Sectional Study

An observational study design where both exposure status and disease outcome status are assessed simultaneously in the present.

Case-Control Study

An observational analytical study design where participants are identified based on outcome status in the present (cases vs. controls) and assessed retrospectively for past exposure.

Prospective Cohort Study

An observational study design that identifies disease-free individuals classified by exposure status in the present and follows them into the future to measure the occurrence of outcomes.