Ipsative assessment

Ipsative (/ˈɪpsətɪv/; Latin: , "of the self") is a descriptor used in psychology to indicate a specific type of measure in which respondents compare two or more desirable options and pick the one that is most preferred (sometimes called a "forced choice" scale). This is contrasted with measures that use Likert-type scales, in which respondents choose the score (e.g. 1 to 5) which best represents the degree to which they agree with a given statement (see also Norm-referenced test). "Ipsative Comparisons" are also sometimes used in standardized testing to compare significant differences in subtest scores.

While mean scores from Likert-type scales can be compared across individuals, scores from an ipsative measure cannot. To explain, if an individual was equally Extroverted and Conscientious and was assessed on a Likert-type scale, each trait would be evaluated singularly, i.e. a respondent would see the item "I enjoy parties." and agree or disagree with it to whatever degree reflected his/her preferences.

If the same traits were evaluated on an ipsative measure, respondents would be forced to choose between the two, i.e. a respondent would see the item "Which of these do you agree with more strongly? a) I like parties. b) I keep my work space neat and tidy." Ipsative measures may be more useful for evaluating traits within an individual, whereas Likert-type scales are more useful for evaluating traits across individuals.

Additionally, ipsative measures may be useful in identifying faking. However, ipsative measures may, especially among testing-naïve individuals exhibiting high levels of conscientiousness and/or neuroticism, decrease test validity by discouraging response and/or encouraging non-response. For example, a test's authors may force respondents to choose between "a) Animals chase me in my dreams" and "b) My dreams are nice" in an effort to see whether a given respondent is more inclined toward "faking bad" or toward "faking good." When faced with such a question, a child frequently terrified by nightmares that rarely if ever involve animals, and especially one whose parents have taught him/her strict rules against lying, may simply refuse to answer the question given that for that respondent nearly all of the time both descriptions are inaccurate. Even a previously presented guideline "Choose the answer that [best/better] describes you" may be unhelpful in such a situation to responders who worry that endorsing one item or the other will still involve stating it to be accurate or "well"-descriptive to some positive degree. Only if the guideline is presented as "Choose the answer that more accurately or less inaccurately describes you" and the above-described responder is sophisticated enough to reason out his/her response in terms of "Despite the infrequency with which I have nice dreams, I have them [more frequently / less infrequently] than dreams in which animals chase me" (or, in theory, vice versa) will such a responder be willing to answer the question — and phrasing the guideline in this way bears its own cost of making the question reveal less about the respondent's propensities because the respondent is no longer forced to "fake" one way or another.

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