The only way that nominal data can be used is to consider frequencies. It is equally as daft to try to do arithmetic with nominal scales where the categories are denoted by numbers: the number 10 takes penalty kicks, and if the England coach found that Jonny Wilkinson (his number 10) was injured he would not get his number 4 to give number 6 a piggyback and then take the kick. A number 10 player is not necessarily better than a number 1 (most managers would not want their fly-half stuck in the front of the scrum!). We could equally have shirts with FH and H instead of 10 and 1. These numbers do not tell us anything other than what position the player plays. England’s Jonny Wilkinson), and the number 1 is always the hooker (the ugly-looking player at the front of the scrum). In rugby, the numbers of shirts denote specific field positions, so the number 10 is always worn by the fly-half (e.g. For example, the numbers worn by players in a rugby or football (soccer) team. However, sometimes numbers are used to denote categories.

It should be obvious that if the variable is made up of names it is pointless to do arithmetic on them (if you multiply a human by a cat, you do not get a hat). When two things that are equivalent in some sense are given the same name (or number), but there are more than two possibilities, the variable is said to be a nominal variable.

In all cases there are just two categories and an entity can be placed into only one of the two categories. Other examples of binary variables are being alive or dead, pregnant or not, and responding ‘yes’ or ‘no’ to a question. In its simplest form it names just two distinct types of things, for example male or female. A categorical variable is one that names distinct entities. You are a human or a cat or a fruit bat: you cannot be a bit of a cat and a bit of a bat, and neither a batman nor (despite many fantasies to the contrary) a catwoman (not even one in a nice PVC suit) exist. A categorical variable that you should be familiar with already is your species (e.g. Why is my evil lecturer forcing me to learn statistics?Ī categorical variable is made up of categories.

Field discovering statistics using spss