There are also two levels of measurement for numerical variables. Interval scale applies to numerical variables with a zero value defined arbitrarily. Temperatures in Celsius are an example; the zero is conveniently defined as the reference temperature at which water freezes. Fahrenheit is also interval scale. Zero does not mean absence of the quantity being measured, and it does not necessarily mean the lowest possible number. Interval data can be counted, ranked, and averaged. However, since zero is arbitrary, ratios are meaningless. That is, a 90 ^∘F is not twice as hot as 45 ^∘F. Ratio scale variable is a numerical variable where the zero is not defined arbitrarily. In a ratio scale, zero is the outcome of a count or measurement representing absence of the quantity. Zero does not have to be a necessary outcome in a given situation; what matters is its meaning in theory (i.e. a person of height zero, height is a ratio type of measurement). Ratio data can be counted, ranked, and averaged. Also ratios are meaningful. Of the following, which represents an interval scale and which represents a ratio scale?

a) Profit byApple Inc. last quarter.
b) Year of birth of a person.
c) Longitude of a volcano.
d) Direction of wind in degrees.
e) Distance from your school to the nearest bus stop.