Whereas variable data can indicate both the direction and size of process variation, attribute data indicates only whether an item passes or fails, not how well or how badly it does so.
Attribute data records either:
Attribute data therefore has only two possible values:
The absence (e.g. failure of a lightbulb to work) or presence (e.g. scratches on paintwork) of the characteristic is then counted, and the results recorded and plotted on an attibute chart.