AQA GCSE Statistics key terms

The arithmetic difference between two percentages. An increase from 20% to 25% is an increase of 5 percentage points.

A value below which approximately a specified percentage of ordered data lies; for example, the 90th percentile marks approximately 90% of the data.

The population-size estimate $N = \frac{Mn}{m}$, where $M$ is the first sample size, $n$ is the second sample size and $m$ is the number of marked individuals in the second sample.

A display in which symbols represent frequencies, with a key stating the value of one whole symbol.

A circular diagram divided into sectors whose angles show the proportions of the total in different categories.

A small-scale trial of a survey used to identify problems before the main collection takes place.

An inactive substance made to resemble the treatment being tested.

The whole group of people or items that a statistical investigation concerns.

The sum of all values in a population divided by the number of values in that population.

A diagram showing how a population is distributed across age groups, usually with male and female populations shown on opposite sides.

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

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

An estimate of an unknown or future value based on patterns in existing data.

Data collected first-hand for the investigation being carried out.

Action taken before a problem occurs to prevent it or reduce its possible effects.

A number from 0 to 1 describing how likely an event or characteristic is, where 0 means impossible and 1 means certain.

A list of every possible value or outcome and its probability. The probabilities add up to 1.

The fraction of a group with a particular characteristic, calculated by dividing the number with that characteristic by the total number in the group.

Data describing qualities or types rather than numerical quantities, such as colours or makes of car.

Monitoring a production process to check that manufactured products meet required standards.

Data consisting of numerical quantities, such as measurements or counts.

One of the three dividing values that split ordered data into four approximately equal parts.

A set of questions used to collect information from respondents.

The required number of members to be selected from a particular group in quota sampling.

Selecting members from specified groups until a required number from each group has been obtained; selection within groups need not be random.

Using chance to decide which participants enter each experimental group.

A list of numbers generated randomly, which can be used to select members of a numbered sampling frame.

Selecting members of a population by chance rather than by personal choice. In simple random sampling, every member has an equal probability of selection.