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A self-report inventory is a type of psychological test in which a person fills out a survey or questionnaire with or without the help of an investigator. Self-report inventories often ask direct questions about personal interests, values, symptoms, behaviors, and traits or personality types. Inventories are different from tests in that there is no objectively correct answer; responses are based on opinions and subjective perceptions. Most self-report inventories are brief and can be taken or administered within five to 15 minutes, although some, such as the Minnesota Multiphasic Personality Inventory (MMPI), can take several hours to fully complete. They are popular because they can be inexpensive to give and to score, and their scores can often show good reliability.
There are three major approaches to developing self-report inventories: theory-guided, factor analysis, and criterion-keyed. Theory-guided inventories are constructed around a theory of personality or a prototype of a construct. Factor analysis uses statistical methods to organize groups of related items into subscales. Criterion-keyed inventories include questions that have been shown to statistically discriminate between a comparison group and a criterion group, such as people with clinical diagnoses of depression versus a control group.
Items could use any of several formats: a Likert scale with ranked options, true-false, or forced choice, although other formats such as sentence completion or visual analog scales are possible. True-false involves questions that the individual denotes as either being true or false about themselves. Forced-choice is a set of statements that require the individual to choose one as being most representative of themselves.
If the inventory includes items from different factors or constructs, the items can be mixed together or kept in groups. Sometimes the way people answer the item will change depending on the context offered by the neighboring items.
Self-report personality inventories
Honesty of response may be the major problem with the self-report personality tests. Test questions are often transparent, and people can usually figure out how to respond to make themselves appear to possess whatever qualities they think the organization wants. In addition, people may falsify good responses, be biased towards their positive characteristics, or falsify bad, stressing negative characteristics, in order to obtain their preferred outcome.
A variety of self-report inventories for assessing anger and aggression have been published.
The biggest problem with self-report inventories is that patients may exaggerate symptoms in order to make their situation seem worse, or they may under-report the severity or frequency of symptoms in order to minimize their problems. For this reason, self-report inventories are more often used primarily for measuring levels of traits, or for symptom severity and change. Inventories should not be used in isolation to diagnose a mental disorder. They should be verified by other assessment data. Clinical discretion is advised for all self-report inventories.
Another issue is the social desirability bias, which can cause over-reporting of socially desirable and under-reporting of socially undesirable behaviors.
Many personality tests, such as the MMPI or the MBTI add questions that are designed to make it difficult for a person to exaggerate traits and symptoms. However, these tests suffer from the inherent problems associated with personality theory and testing, in that personality is a fluid concept that can be difficult to define.