Statistical data comes in one ogf two broad types Qualitative and Quantitative. Qualitative data is descriptive – a colour, type or one of a category.

The categories that describe qualitative data may be ordered or not. We may order colours in order of their appearance in the spectrum – red/orange/yellow/green/blue/indigo/violet. If the categories are not ordered they are said to be nominal.

When the categories are ordered, they are said to be ordinal. Ordinal categories may be ones that record size small/medium/large or level of agreement disagree/indifferent/agree. Often these categories are subjective.

Quantitative data is numerical. Telephone numbers and body weights are both quantitative. Quantitative data may be continuous or not, accurate or not. Telephone numbers are discrete numbers are a persons weight cannot be recorded to any number of decimal places – a persons weight mau be recorded to the nearest pound, and is anyway variable throughout the day.

Quantitative data may be coded numerically for computer storage. We may label colours with numbers

red 1

orange 2

yellow 3

green 4

blue 5

indigo 6

violet 7

The data is stored as a series of numbers but remains quantitative.

On the other hand, each colour of light has a wavelength. If colour is recorded by its wavelength, this is quantitative. Data can sometimes be recorded as both qualitative and quantittive data. Usually data that can be recorded in both forms contains more information if recorded as quantitative data.