Organisation of Data
Continuous and discrete variables
Decide whether a variable is continuous or discrete.
Quantitative characteristics are variables, and they come in two types.
A continuous variable can take any value within a range: whole numbers, fractions, and even values like √2 = 1.414… Height, weight, time and distance are continuous. A child's height can be 120 cm, 120.5 cm, 120.53 cm, and so on, with no gaps.
A discrete variable can take only certain values, and changes in jumps. The number of students in a class can be 25 or 26, but never 25.5; the number of cars in a car park, the number of rooms in a house.
Careful: a discrete variable can take fractional values, as long as it cannot take the values in between them. Shoe sizes come in 6, 6½, 7, 7½… but there is no size 6¼. So shoe size is discrete, even though it includes fractions.
The test is simple: can a value in between exist? If yes, the variable is continuous; if no, it is discrete.
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