Term
Definition
Variable
Any characteristic or attribute that can vary among subjects in a study.
Independent variable
The variable that is manipulated or categorized to observe its effect on the dependent variable.
Dependent variable
The outcome variable measured to assess the effect of the independent variable.
Confounding variable
An extraneous variable that affects both the independent and dependent variables
Bias
Systematic error that leads to an incorrect estimate of effect or association.
Selection bias
Bias arising when study participants are not representative of the target population
Information bias
Bias caused by errors in measuring exposure
Random error
Variability in data due to chance
Cohort study
An observational study following a group of individuals over time to assess exposure-outcome relationships.
Case-control study
An observational study comparing individuals with a condition (cases) to those without (controls) to identify potential risk factors.
Cross-sectional study
An observational study measuring exposure and outcome at a single point in time to assess prevalence or associations.
Experimental study
A study in which researchers actively manipulate variables to assess causal effects
Randomized controlled trial (RCT)
An experimental study where participants are randomly assigned to intervention or control groups to reduce bias and establish causality.
Blinding
Keeping participants
Placebo effect
Improvement in a participant’s condition due to expectations rather than the active intervention.
Internal validity
The extent to which study results accurately reflect the true relationship between exposure and outcome within the study population.
External validity
The extent to which study findings can be generalized to other populations
Confounding
Distortion of the apparent effect of an exposure on an outcome caused by a third variable associated with both.
Control of confounding
Methods to reduce confounding
Data presentation
The organized display of research data in tables
Frequency distribution
A summary of how often each value occurs in a dataset; often displayed in a table or histogram.
Histogram
A graphical representation of the distribution of numerical data using bars to show frequency of values within intervals.
Bar graph
A chart that uses bars to compare categorical data; bar heights represent the magnitude of each category.