Classifying Data
Interval Level
Numbers measured in the interval level have properties of both the nominal and ordinal levels because they can be classified by name and arranged in a certain order.
The difference of measurements in the interval level is that the distances between the intervals on the scale are equal along the interval scale from the lowest value to the highest value. Furthermore, with interval measurements, the lowest value does not have a true zero value; instead, an arbitrary zero or a value of 1 is assigned.
Examples:
Some common examples are temperature expressed in Celsius and calendar years.
Take a look at a laboratory thermometer with a Celsius scale. You will notice that the thermometer is divided into 100 equal divisions or intervals with 0°C as the temperature at which water freezes and not the lowest temperature or the absence of a temperature reading, while 100°C is the temperature at which water boils. The zero in the thermometer is an arbitrary zero because there are still values lower than 0°C that can take negative values.
Ratio Level
The measured values in the ratio level have properties of the nominal, ordinal, and interval levels as well as a true or actual zero value. Science quantities such as height, weight, volume, mass, distance, speed, energy, and temperature on the Kelvin scale are some examples.
The ratio level is the most precise level because it can be measured by using a standard measuring instrument with a true zero value.
