Social Research Glossary


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Citation reference: Harvey, L., 2012-20, Social Research Glossary, Quality Research International,

This is a dynamic glossary and the author would welcome any e-mail suggestions for additions or amendments. Page updated 19 December, 2019 , © Lee Harvey 2012–2020.


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core definition

Probability measures how likely an event will occur.

explanatory context

Probability is a measure or estimation of how likely it is that something will happen or that a statement is true (sometimes the term likelihood is used).

Event is used as a shorthand for 'something will happen or something is true'.

The probability of an event never happening is given the value sero. The probability of it always happening is given the value 1. (Thus throwing a standard die, the probability of a 7 or more is zero while the probablity of 6 or less is 1).

The probability of most events lies between 1 and 0, (such as the probability of throwing a 3, 4 or 5 with a standard die is 3 in 6 (3/6 or 0.5).

Probability theory is used to work out the extent to which results based on a sample are indicative of the results for the population w=from which the sample was taken.

analytical review

Colorado State University (1993–2013) defines probability as:

The chance that a phenomenon has a of occurring randomly. As a statistical measure, it shown as p (the "p" factor).

Easton and McColl (undated) wrote:

A probability provides a quantatative description of the likely occurrence of a particular event. Probability is conventionally expressed on a scale from 0 to 1; a rare event has a probability close to 0, a very common event has a probability close to 1.

The probability of an event has been defined as its long-run relative frequency. It has also been thought of as a personal degree of belief that a particular event will occur (subjective probability).

In some experiments, all outcomes are equally likely. For example if you were to choose one winner in a raffle from a hat, all raffle ticket holders are equally likely to win, that is, they have the same probability of their ticket being chosen. This is the equally-likely outcomes model and is defined to be:
P(E) = (number of outcomes corresponding to event E)/( total number of outcomes)....

associated issues


related areas

See also

confidence interval

normal distribution


sampling error

significance tests


Researching the Real World Section for analysing survey sample data


Colorado State University, 1993–2013, Glossary of Key Terms available at, accessed 16 March 2013, still available 1 June 2019.

Easton, V and McColl, J.H., undated, available at, accessed 28 March 2013, still available 12 June 2019.

copyright Lee Harvey 2012–2020


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