Is a sample that has not been drawn in the exact proportion to the universe.

A sample that is not representative of the population to which generalizations are to be made.

a statistical sample in which members of the statistical population are not equally likely to be chosen

Samples which are collected at locations based on historical information; behavior of contaminants or; knowledge about the physical system's matrix (the physical system's effect on fate of transport).

sample that is not representative of the population from which it was drawn (see Representative Sample).

Any sample which is not a random sample. AN random sample. BT sample. RT stratified sample, systematic sample.