3.8 Quality measure

What this heading covers

The definition is short and it settles an argument that runs through every measurement programme. A single count is not a quality measure. A quality measure combines at least two quality measure elements through a measurement function, which is an algorithm or calculation. That is why the draft can speak of measures for a subcharacteristic and mean something reproducible: the elements are defined properties with a measurement method, and the function fixes how they combine. The definition also separates inherent measures, which quantify structural properties of the product, from behavioural measures, which quantify properties seen when the product is used. A team that reports one number without its elements and its function has a figure, not a quality measure.

Record position: measurement concept 1 of 3, from the fifteen terms in clause 3.

What the heading asks of a team

What to put in place before publication

1. Write every reported measure as a formula with named elements, not as a label on a dashboard.
2. Record the population behind each element, because a ratio with an unstated denominator cannot be compared over time.
3. Label each measure as inherent or behavioural, and keep the two kinds apart in a report.
4. Store the measure definition beside the result, so a reader can recompute it.
5. Version the definition, and date the change when a function or a population changes.

Where teams usually fall short

• A dashboard tile called quality with no formula and no population behind it.
• A measure whose denominator changed between releases, so the trend is an artefact of the change.

What happens next

The quality measure element page takes the definition apart, and the measurement function page explains the arithmetic that turns elements into a measure.