Question 3: What kind of variable is reaction to the treatment? What does this graph actually show?
We divide the children into separate categories, ‘no discomfort’, ‘mild reaction’, ‘winced’, ‘cried’, and ‘screamed’. These have no numerical value, we therefore have a qualitative or categorical variable. The categories are clearly ordered, from ‘no discomfort’ to ‘screamed’. We therefore have an ordered categorical variable, or ordinal variable.
The graph shows the cumulative reaction. The first pair of bars shows the proportions reporting no discomfort, the second pair shows the proportions reporting no discomfort or mild reaction, the third pair shows no discomfort or mild reaction or winced, and so on. The fifth pair shows all children and is 100% by definition.
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