Edexcel GCSE Statistics key terms

The arithmetic mean of seasonal variations for the same season or corresponding point in successive cycles; also called estimated mean seasonal variation or average seasonal effect.

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

A summary describing how spread out the values in a data set are.

The value that divides a distribution into two halves, with half the values below it and half above it.

A recorded value or answer that is absent from a data set.

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

The value at the highest point of a normal distribution's curve, where values are most concentrated.

A relationship in which one variable consistently increases, or consistently decreases, as the other increases. The pattern need not be a straight line.

The mean of a fixed number of successive observations, recalculated as the group moves forward through a time series.

A chart with two or more bars side by side for each category, allowing data sets to be compared.

Matched sets of values for three or more variables, recorded for each individual, object or observation. This term is assessed at Higher tier only.

Events that cannot both occur in the same trial. For two mutually exclusive events, $P(A \text{ and } B)=0$.

An investigation of naturally occurring conditions or differences, without the researcher setting or manipulating those conditions.

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

A distribution shape with a longer tail towards lower values, usually shown on the left.

Failure to obtain any response from a selected person or organisation, for example because they cannot be contacted or do not return a questionnaire.

Bias arising when those who respond differ in relevant ways from those who do not respond.

A probability distribution for continuous quantities with a symmetrical, bell-shaped curve and equal mean, median and mode.

A method of collecting data by watching and recording what happens.

The number of times an outcome or event actually occurs in an experiment.

A class interval with no specified lower boundary or no specified upper boundary.

A question that lets a respondent answer in their own words without choosing from a supplied set of answers.

Selecting suitable members of a population who are readily available. Also called convenience sampling.

Data that can be placed in a meaningful order or given a numerical rating scale, such as league positions or satisfaction ratings.

A possible result of a random experiment, such as HT when two coins are tossed in order.

A data value that lies unusually far from the general pattern of the other values. It may be genuine or caused by an error.

A calculated limit used to identify unusually small or large values. Values beyond the limit are classified as outliers under the chosen rule.

Two values belonging to the same person, object or observation, one for each variable.