Normative Versus Ipsative Measurement

Normative Measurement

Normative measurement usually presents one statement at a time and allows respondents using a five-point Likert-type scale to indicate the level of agreement they feel with that statement. Here is an example:

“I keep my spirits up despite setbacks.”

Such a rating scale allows quantification of individuals' feelings and perceptions on certain topics. Scoring of normative scales is fairly straightforward. Positively phrased items get a 5 when marked as Strongly agree, and negatively phrased items need to be recoded accordingly and get a 5 when marked as Strongly disagree. Despite occasional debates on the ordinal versus interval nature of such normative scales, scores of similar items are usually combined into a scale score and used to calculate means and standard deviations, so norms can be established to facilitate interpersonal comparisons. The normative scores can be submitted to most statistical procedures without violating the assumptions assuming the normative scores are accepted as interval-level measurements.

Ipsative Measurement

Ipsative measurement presents an alternative format that has been in use since the 1950s. Ipsative measures are also referred to as forced-choice techniques. An ipsative measurement presents respondents with options of equal desirability; thus, the responses are less likely to be confounded by social desirability. Respondents are forced to choose one option that is “most true” of them and choose another one that is “least true” of them. A major underlying assumption is that when respondents are forced to choose among four equally desirable options, the one option that is most true of them will tend to be perceived as more positive. Similarly, when forced to choose one that is least true of them, those to whom one of the options is less applicable will tend to perceive it as less positive. For example, consider the following:

• a.
  prefers to keep active at work.
• b.
  establishes good compromises.
• c.
  appreciates literature.
• d.
  keeps my spirits up despite setbacks.

The scoring of an ipsative scale is not as intuitive as a normative scale. There are four options in each item. Each option belongs to a specific scale (i.e., independence, social confidence, introversion, or optimism). Each option chosen as most true earns two points for the scale to which it belongs; least true, zero points; and the two unchosen ones each receive one point. High scores reflect relative preferences/strengths within the person among different scales; therefore, scores reflect intrapersonal comparisons.

In an ipsative questionnaire, the sum of the total scores from each respondent across all scales adds to a constant. This creates a measurement dependency problem. For example, if there are 100 items in an ipsative questionnaire with four options for each item, the total score for each participant always adds up to be 400. Because the sum adds to a constant, the degree of freedom for a set of m scales is (m − 1), where m is the number of scales in the questionnaire. As long as the scores on m − 1 scales are known, the score on the mth scale can be determined. The measurement dependency violates one of the basic assumptions of classical test theory—independence of error variance—which has implications for the statistical analysis of ipsative scores, as well as for their interpretation.

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