Continuous variables

Some examples of continuous variables are:

• time in minutes to get to school
• length in centimetres of the right foot of year 7 girls
• age in years
• amount in dollars of weekly allowance.

All continuous data need units, and observations are recorded in the desired units.

Continuous variables can take any values in intervals. For example:

• if someone says their height is 149 cm, they mean their height lies between 148.5 cm and 149.5 cm
• if they say their height is 148.5 cm, they mean their height is in between 148.45 cm and 148.55 cm
• if someone reports their age as 14 years, they (usually) mean their age is in between 14 and 15 years.

Note the convention with age is that the interval is from our age in a whole number of years up to the next whole number of years. Our specification of intervals in talking about age is usually not as definite as when we quote someone's height, but the principle is the same − observations of continuous variables are never exact and correspond to intervals, no matter what the size of the interval.