The California Psychological Inventory (CPI) has been:

• Extensively studied and validated
• Involved in longitudinal studies over time
• Revised several times and updated
• Internationally researched for transferability to different cultures
• Developed on the basis of an “empirical keying” strategy
• Used successfully in NZ for over 30 years and internationally for many more years

Niche Consulting has developed its own NZ norms for the CPI from well over 10,000 business people, which allows a comparison of the individual against an appropriate business group on this tool.

A major strength of the CPI concerns the way in which it was developed.  Most of the scales were developed using an “empirical keying” strategy. 

What this means is that the scales were devised based on a comparison of what the scales suggested about an individual, with the way observers described them, and a measurement of their performance.

Theoretically, scales developed in this way have:

1. A much greater likelihood of accurately predicting actual behaviour. 
2. Are more likely to reflect the way others see them rather than how the individual sees themselves
3. Are more useful in predicting behaviour especially in individuals who have little self perception or a lack of appreciation of their own strengths and weaknesses. 

The CPI has been designed based on an instrumental standpoint, meaning evaluation of whether a scale is useful or valid has more to do with the outcome of the test than the “look” or “face validity” of the items being asked. 

Low “face validity” of a test has the following outcomes:

• People can find it difficult to know what the questions are related to.
  
• This has a major benefit as it makes the questionnaire more difficult to “fake” or manipulate. 

An instrumentally constructed test uses the score on the test to classify people in a way others classify them and the accuracy with which scores in the test predict or confirm the behaviour that is relevant to the test. 

Scales developed by instrumental criteria often contain a mix of both obvious and subtle items.

• A subtle item is an item might be “I like Alice in wonderland”
  
• An obvious item may be “I enjoy social gatherings just to be with people”. 

When interpreting the CPI we are never looking at individual answers but looking for the trends on each scale and what that means in terms of how the individual may be described by the people who know them.

The CPI also has many more items relating to any one scale (usually between 28-40 items) than most personality tools (typically only 8 items). 

The complexity of the tool comes from the way the test is constructed and that the 20 personality scales are very broad and overlap. 

This means the whole profile should be interpreted rather than single scales in isolation.   Tools such as OPQ, HPI or 15FQ on the other hand have very narrow scales, which are meant to have no overlap.

Buros Test Review Abstract about the CPI

Buros Institute of Mental Measurement does a peer review of assessments where the scientific rigor of test development is reviewed, this is where experts “test” the test makers.

“Over the nearly five decades since the creation of the CPI, an extensive body of research has formed that examines its performance in diverse assessment populations and age groups. This body of knowledge provides a wealth of comparative reference materials."

"The CPI provides a substantiated method to aid in the consensual description of differences between individuals and groups across many substantiated dimensions of personality. Since its inception, the CPI has been quite successful in its groundbreaking attempt to describe a broad array of fairly robust personality characteristics across a wide cross section of society.”