Edexcel GCSE Statistics key terms

Data organised into groups, often numerical class intervals, with a frequency recorded for each group.

A diagram for grouped continuous data in which bars cover the class intervals and bar areas represent frequencies.

A statement that can be tested by collecting relevant data and analysing it appropriately.

An event that cannot happen; its probability is 0, or 0%.

A response that supplies some of the requested information but leaves other parts unanswered.

A way of recording a value that does not match the required form, such as using the wrong unit or putting a decimal point in the wrong place.

Events for which knowing whether one occurs does not change the probability of the other occurring.

Trials for which knowing the outcome of one does not change the probabilities of outcomes on another.

A number expressing a value relative to a comparison value set equal to 100. It has no units.

A judgement extending beyond the collected data, such as using a sample to suggest something about a population.

An increase in the general level of prices over time, commonly measured using the annual percentage change in CPI.

The ninth decile minus the first decile, $D_9-D_1=P_{90}-P_{10}$, measuring the spread of the middle 80% of values.

The difference between two specified percentiles. For example, $P_{90}-P_{10}$ measures the spread of the middle 80% of values.

Estimating a value using a model within the range of the observed input values.

The upper quartile minus the lower quartile, $Q_3-Q_1$, measuring the spread of the middle 50% of ordered values.

The event consisting of outcomes common to both events. It is written $A \text{ and } B$, or $A\cap B$.

An influence of an interviewer's opinions, expectations or manner of asking questions on the answers respondents give.

A process in which stages are repeated, with improvements informed by what was learnt during earlier attempts.

The probability that two events both occur, written $P(A\text{ and }B)$.

Selecting members of a population using the researcher's judgement about who will represent it.

An explanation of what the colours, shades, patterns or symbols in a diagram represent.

An experiment conducted in a controlled environment, where the researcher can control conditions and variables.

A question whose wording suggests or encourages a particular answer.

The extent to which a researcher can set or keep constant the conditions and variables in an investigation.

A relationship in which the points on a scatter diagram follow a straight-line pattern.

Estimating a value between two known values by assuming a constant rate of change between them.

A straight line drawn through a scatter diagram to summarise an approximately linear relationship between two variables and make estimates.

The value marking the lower quarter of an ordered dataset, written as $\text{LQ}$.