AQA GCSE Statistics key terms

The difference between the two ranks belonging to one pair of values, usually written $d$.

A measure expressing one quantity relative to another, such as the number of deaths during a year per 1,000 people.

A measure of how much a quantity changes over a specified interval, or the frequency of an event in a stated population during a stated period. Its units explain which meaning applies.

Data as originally collected or recorded, before checking, cleaning or further processing.

An original data value, before it has been converted into a standardised score.

An existing publication, record or database used to obtain secondary data.

A line of best fit determined by a statistical calculation rather than by eye, usually written as $y=a+bx$.

The proportion of trials in which an event occurs: $\text{relative frequency}=\frac{\text{frequency of the event}}{\text{total number of trials}}$.

The ratio of the absolute risk in one group to the absolute risk in a comparison group: $\text{relative risk of A compared with B}=\frac{p_A}{p_B}$.

The extent to which findings can be trusted, taking account of the sample, data quality and variation.

Repeating an investigation using a fresh sample and comparable methods and conditions to check whether similar findings are obtained.

A way of organising or displaying data, such as a table, chart or graph.

A sample that reflects the relevant characteristics of the population being investigated.

A person who answers questions in a questionnaire or interview.

The variable measured as the outcome of an investigation, whose differences are being investigated in relation to an explanatory variable. Also called the dependent variable.

A weighted index tracking changes in retail prices across a range of goods and services.

A group selected from a population to provide data about that population.

The total of the values in a sample divided by the number of values in that sample.

The difference between the largest and smallest measurements in a sample.

The number of people, items or observations included in a sample.

The set of all possible outcomes of a probability experiment.

An organised display of all possible outcomes, often using a grid when combining two experiments.

The process of selecting part of a population to collect data from.

A tendency for a selection method to favour or exclude particular parts of the population, potentially distorting conclusions.

A list of all the members of the population from which a sample can be selected.

The differences in statistical results between samples from the same population caused by which members happen to be selected.

A graph of paired numerical measurements, with one point for each observation, used to investigate a relationship between two variables.