But a small group of American statisticians was beginning to use probability sampling, in which interviewees are chosen by a random process outside the interviewer's control.

Further developments, such as unequal probability sampling, arose.

Because the survey presented the opinions of a select group of scientists, the technique of probability sampling was not used.

Not all samples are selected by probability sampling (e.g. the WHO collaborative studies).

Standard techniques like probability sampling, and concepts like focus groups, were either developed at National Analysts or saw some of their earliest application.

Twelve-step groups, like AA, are not conducive to probability sampling of members.

Performing nonprobability sampling can be considerably less expensive than doing probability sampling.

Surveys that are not based on probability sampling have greater difficulty measuring their bias or sampling error.

In academic and government survey research, probability sampling is a standard procedure.

These various ways of probability sampling have two things in common: