Ordinal

Ordinal scales have the property of magnitude as well as identity. The numbers represent a quality being measured (identity) and can tell us whether a case has more of the quality measured or less of the quality measured than another case (magnitude). We will discuss three important concepts in this section. We will look at two different forms of ordinal scales -- ranked preferences and likert ratings. We will end with a discussion of the interval or distance between scale points.

Ranked Preferences

Physiological psychologists are often interested in preferences for different tastes. Let's say that you were asked to taste five different foods and rank your preference in order. The foods are sweet, salty, bitter, sour, fatty. We usually rank our strongest preference as "1" . With five foods, our lowest preference would be "5". These ranks have the property of identity because they tell us which food and magnitude because they place the preference in order. They do not tell us "how much" more, just more or less.

Because of the property of magnitude (or order), the numbers are no longer considered arbitrary. The numbers reflect a characteristic of the person -- taste preference. Let's change the numbers assigned to "Sweet" and "Fatty" and "Sour" for our first student.

Changing the numbers changes the meaning -- the numbers now indicate a very different type of person -- rather than having a "sweet tooth" we would think of this student as having an unusual taste preference.

Likert Ratings

Likert ratings are used in surveys where we are asked to rate how much we agree or disagree with a statement. They are classified as ordinal scales because they have the properties of identity and order. They have the property of identity because they let us know whether we agree or disagree. They also have the property of order because each number represents a rating that is more or less than the others.

Listed below is an item from a survey about relationships. We are asked to rate how much the item describes how we feel in our important relationships.

A. It is easy for me to become emotionally close to others. I am comfortable depending on them and having them depend on me. I don't worry about being alone or having others not accept me.

This person chose a number that is almost the highest possible. We would consider this a high ranking or "strong" agreement with the statement.

Let's see what happens if we switch the numbers around.

On this scale, the number "6" no longer has the meaning of strongly agreeing with the statement. In fact, it does not have a clear meaning at all.

The order of numbers must be constant in either ascending or descending order.

Distance Between Scale Points

We assume that the intervals between scale points on ordinal scales are unequal. Thus, the "distance" between a rank of "1" and "2" is not necessarily the same as the "distance" between ranks of "3" and "4".

Let's say that for the ranked preferences, our second student liked fatty tastes the best but also has a strong liking for salty foods which he rated as "2". He likes sweet foods (rated "3") but has a stronger preference for foods such as French fries and potato chips that are both fatty and salty. He does not like sour foods (rated "4") and really hates bitter tastes (rated "5"). In this case the preference "distance" between "3" and "4" is much greater than the preference "distance" between ranks "1" and "2". The psychological distance represented by the interval between numbers is not equal.

Let's look at the same issue for likert scales. The psychological distance between "1" (Not at All Like Me) and "4" (Somewhat Like Me) is not the same as between "4" (Somewhat Like Me) and "7" (Very Much Like Me) even though there is a difference of 3 points between each rating. Research suggests that our willingness to endorse positive statements is different from our willingness to endorse negative statements. We are also less likely to endorse statements at the extreme ends (e.g., "1" and "7") than at a more "moderate" level (e.g., "2" and "6"). Thus, the psychological distance represented by the interval between numbers is not equal.

Other examples of ordinal scales in psychological research: Class rank, dominance hierarchies.