MBTI® Form M

MBTI® Form M
Isabel Briggs Myers and Katherine C. Briggs

IMPORTANT ENHANCEMENT: FORM M EDITION

The revised MBTI, Form M, implements a new item development and scoring method based on item response theory (IRT), one of the most powerful components of modern test theory. The MBTI has the distinction of being the first widely used personality instrument to be developed and scored using IRT-based methods. In addition, the revision stems from a fresh look at every report and support piece. The result: a more accurate, reliable instrument presented in an improved format with up-do-date information on psychological type.

The revision itself was undertaken with the strongest possible commitment to maintaining the integrity of the instrument, its theoretical base, and its empirical tradition. Concurrently, the most up-to-date psychometric knowledge was explored and implemented, in the tradition of Isabel Myer's own pioneering work.

IRT: A GREATER LEVEL OF ACCURACY

The decision to use the IRT with the MBTI was made after a nationwide study of over 2,400 adults compared the previous method, in which item weights are derived from prediction ratios, and a new IRT-based method. The results were clear: the IRT-based method yielded the better estimate of a person's best-fit type. No matter which groups were examined, IRT consistently provided more accurate prediction.

Because of these findings, the IRT-based method was the primary method used to select the items that make up the revised MBTI, Form M, and it is applied in the scoring process to arrive at the best possible prediction of a client's four true preferences. This development represents an important advance in type measurement.

ITEMS SELECTED FOR MAXIMUM INFORMATION VALUE

Additional criteria were used in analyzing the items. Information gained from using both the IRT-based method and the existing prediction ratio-based method was used in selecting the final items for the revised MBTI. The IRT approach to item selection provided answers to these questions:

• How well does this item sort people with different preferences into the correct categories?
• How well does this item sort people into their appropriate categories exactly at the midpoint of the scale?
• Has the social desirability affected the response to the item-and, if so, how can this be taken into account?

The answers to these questions led to an extra degree of accuracy built into the MBTI.

FEWER ITEMS, GREATER RELIABILITY

One of the advantages of the IRT is that it provides extensive information about how each item is performing. This makes it possible to choose the items that can provide the most information. The end result is that the IRT makes even greater reliability possible, even with fewer items. Administrators of the MBTI can now be more confident that its items are sensitive to a given client's preferences.

SCORING MORE REFINED, MORE POWERFUL

To arrive at a prediction of a client's preference on any given scale, IRT takes into account the client's response pattern across an entire set of items. Those that provide the most information- in other words, items that do the best job of discriminating between opposite preferences at the midpoint of the scale- are assigned higher weights. Because IRT methodology uses all of the information available about an item to assign weights, it is much more refined and powerful than the prediction ratio method or any other item-rating method.

MORE ACCURATE CLASSIFICATION WHERE IT'S MOST CHALLENGING

It's fairly easy to arrive at the correct preference on a given scale when clients are clear about their preference. Correctly classifying those clients who fall near the midpoint of the scale is more challenging. IRT provides a powerful means for arriving at a correct classification. As an administrator of the revised MBTI, you can be confident that you are using the most sophisticated method available for predicting a person's basic preferences.

GENDER-DIFFERENT SCORING COMPLETELY ELIMINATED

Testing standards recommend that items showing gender bias be detected and eliminated. Therefore, we analyzed every item in the MBTI, excluding from the new form each item that was found to contain gender bias. The result: the revised MBTI has no scales with different weights for men and women. Interpretation is now simpler, and both template and hand scoring are much easier.

SUMMARY

The revised MBTI, Form M, is your most powerful instrument for positive type identification, planning, and counseling. Use it in every situation you've ever counted on the MBTI to resolve or improve, with even more accuracy and even more confidence. The revised MBTI is a change whose time has definitely come.