AQA GCSE Statistics key terms

A summary value describing the centre or a typical value of a dataset, such as its mean, median or mode.

A numerical description of how much the values in a dataset vary. Examples include the range, interquartile range and standard deviation.

The middle value of ordered data, or the mean of the two middle values when there is an even number of values.

Combining several existing categories into a broader category, so their separate identities are no longer shown in the summary.

A value that has not been recorded or is unavailable.

The class interval with the highest frequency in a grouped frequency table.

The class interval with the greatest frequency in grouped data; also called the modal class.

The data value or category with the greatest frequency.

The mean of a fixed number of consecutive observations, recalculated as the group moves forward one observation at a time.

A bar chart with several bars side by side for each category, comparing more than two data sets.

Data recording more than two variables for each individual or object, with the values kept together as a set.

Events that cannot both occur in the same trial.

An investigation of the effects of a change that occurs without the researcher deliberately producing it.

An association in which larger values of one variable tend to occur with smaller values of the other.

A distribution with a longer tail towards lower values, usually with most values concentrated towards the higher end.

A classification used when there is no clear overall trend. AQA uses this description for coefficients strictly between $-0.2$ and $0.2$.

Failure to obtain a response from a selected member of a sample, for example because they do not return a questionnaire or cannot be contacted.

A symmetrical, bell-shaped probability distribution for a continuous quantity, with most values near the mean.

Collecting data by watching or measuring events and recording what happens.

A class interval with no stated lower boundary or no stated upper boundary, such as $x \geq 90$.

A question that allows a respondent to give their own answer without choosing from a fixed set of options.

Selecting readily available members of the population who meet the study criteria; also called convenience sampling.

Categorical data whose categories have a meaningful order, such as responses from strongly disagree to strongly agree.

A possible result of a probability experiment, such as heads on a coin toss.

An extreme data value that does not fit the general pattern of the other values.

A calculated limit beyond which a data value is classified as an outlier using a chosen rule.

A measure of the strength and direction of a linear relationship between two variables, commonly written as $r$.