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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Normal distribution

core definition

A normal distribution is a bell-shaped frequency distribution curve reflecting the occurence of human attributes as well as representing sampling distributions, which is an important element of probability theory.

explanatory context

A normal distribution is a bell-shaped frequency distribution curve that is often obtained when human characteristics are measured and plotted. For example, height shows an approximately normal distribution: most adults are of medium height while a few are short and a few are tall, so that when height is plotted against frequency something close to the bell-shaped normal curve is obtained. The normal distribution is a mathematically defined curve, however.


The normal distribution has some very useful features that are important in probability theory. Most importantly, for statistical analysis some sampling distributions are approximately normally distributed. This enables estimates of sampling variation and hence sampling error to be made. In effect it allow us to estimate how close the results from a sample are to the true figures for the population.

analytical review

associated issues

Normal distribution and formula. Note that the normal distribution is a function of the standard deviation of the distribution and there is a constant proportion of the area under the curve for ach standard deviation from the mean, which is at the centre.

related areas

See also

sampling error

significance test


copyright Lee Harvey 2012–2020


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