Sampling bias

Sampling bias is systematic distortion in how observations are selected, making a sample unrepresentative of the population being studied.

Selection bias: Selection bias occurs when inclusion in a study depends on characteristics related to its outcomes or target population. Sampling bias is one form of selection bias, arising specifically from how a sample is drawn.
Statistical population: A statistical population is the complete set of units about which an analysis seeks to draw conclusions. Representativeness is judged against the population the study intends to describe.
External validity: External validity is the extent to which study findings apply beyond the studied sample, setting, or conditions. A distorted sample weakens the case for generalizing findings to the target population.
Sampling error: Sampling error is random variation between a sample estimate and the corresponding population value. Unlike bias, sampling error can shrink with larger probability samples.
Nonresponse bias: Nonresponse bias arises when people who do not participate differ systematically from those who do. A sample can become distorted when selected individuals decline or fail to respond.
Sample (statistics): A statistical sample is a subset of units observed from a population for analysis. Sampling bias concerns how this subset differs systematically from its population.
Nonresponse error: Nonresponse error is the difference caused when survey outcomes depend on whether selected people respond. It measures a key pathway by which participation patterns distort survey estimates.
Measurement bias: Measurement bias is systematic error in how a variable is observed or recorded. It distorts recorded values rather than determining which units enter the sample.
Survivorship bias: Survivorship bias results from studying cases that persist while overlooking those that failed or disappeared. Sampling only surviving cases excludes outcomes that would change the apparent pattern.
Sampling frame: A sampling frame is the operational list or procedure from which units are selected for a study. Errors in the frame can exclude population members before selection begins.

Linked from 31 pages