Probability sample in social science research is a sample drawn from a population using methods which ensure random selection. In Probability sample, each member of the population must have an equal probability of being drawn. A probability sample is a sample in which every unit in the population has a chance of being selected in the sample, and this probability can be accurately determined. The combination of these traits makes it possible to produce unbiased estimates of population totals, by weighting sampled units according to their probability of selection.

Nonprobability sampling is any sampling method where some elements of the population have no chance of selection, or where the probability of selection can't be accurately determined. It involves the selection of elements based on assumptions regarding the population of interest, which forms the criteria for selection.

**Probability and sampling** - J S Bulman & J F Osborn.
The concept of probability is introduced, and the role of probability distributions in
statistical theory is discussed, with particular reference to the Normal distribution and
its characteristics.

**Probability Sample Designs that Impose Models on
Survey Data** - Stephen Woodruff.

Abstract: For a substantial class of sampling problems, the sample design and the
characteristics of the population being sampled, not only provide the probabilities of
selection but also impose a regression model on the sample data.

**Survey non-response in a national area
probability sample as a dimension of survey quality; an analysis of community
characteristics** - Kim, Jibum. and Sokolowski, John.

Abstract: Most area probability surveys collect little to no information about
non-respondents. This paper aims to explore the community characteristics of survey
non-respondents in a nation area probability survey. Data selected for use is obtained
from the 2004 General Social Survey, an area probability sample of 6260 housing units. This paper examines community characteristics in
relation to survey non-response and proposes ways to improve response rates among high
non-response communities in national area probability sample surveys.