Sample

A selection from the whole population

Primary Data

Data which is collected for a specific investigation

Standard Deviation

Square root of variance

Qualitative Data

Data which can be organised into categories but cannot be given a numerical value

Lower Quartile

The item one quarter of the way through when the data are put in order

Continuous data

Data which can be measured and which can take any value within a certain range

Discrete data

Data which can have only certain definite values

Mode

The most common

Median

The middle item when the data are in order

Secondary data

Data which is already published and which may be accessed for many investigations

Quantitative data

Data which can be measured or which has an exact numerical value

Interquartile Range

Upper quartile - Lower quartile

Upper quartile

The item three quarters of the way through when the data are put in order

Standard deviation

Tells us how much the data spread out around the mean

Mean

A measure of the average which uses all the data values

Range

The difference between the largest and smallest data values

Population

The whole group that we are interested in

Interquartlie range

Tells us the spread of the middle 50% of the data values