The Sixteen Personality Factor Questionnaire (16PF; Cattell, Eber, & Tatsuoka, 1970) and its companion questionnaires for younger persons, the High School Personality Questionnaire (HSPQ; Cattell, Cattell, & Johns, 1984) and the Children's Personality Questionnaire (CPQ; Porter, Cattell, & Staff, 1975), published by The Institute for Personality and Ability Testing (IPAT), are useful to counselors in that they provide a sample of the client's verbal self-presentation that is broad based and structured. The parent instrument of the three, the 16PF, is consistently ranked among the most used and recommended personality questionnaires (Piotrowski & Keller, 1989), and it ranks high among personality questionnaires in the number of research articles that make reference to it (see, for example, Graham & Lilly, 1984, p. 234).

Several books have been published on the 16PF that are recommended to the practitioner. Karson and O'Dell's (1976) Guide to the Clinical Use of the 16PF deserves mention as a book for practitioners, as does Heather Cattell's (1989) The 16PF: Personality in Depth. Krug's (1981) Interpreting 16PF Profiles provides a unique approach, as a compendium of data about various typical patterns of 16PF scores. Krug's (1977) Psychological Assessment in Medicine, though a bit dated, gives the practitioner a solid grasp of the interaction of 16PF variables and physical well-being. For the counselor in primarily clinical settings, Meyer's (1989) Clinician's Handbook puts scores from the 16PF and other popular tests in the context of Diagnostic and Statistical Manual of Mental Disorders, revised edition, (DSM-III-R; American Psychiatric Association, 1987) diagnosis and treatment.

Background
To understand the place of the 16PF in the field of human assessment generally, it is helpful to think of three domains:
Ability -- This is the domain of what a person can do--his or her talents, skills, proficiencies. The archetypal statement in this realm is "I can do X."
Motive -- This is the domain of movement, drive, or tendency toward something or someone. The archetypal statement in this realm is "In this circumstance, I want X."
Personality -- This is the domain of personal style. The archetypal statement in this realm is "In this circumstance, I am X."
Again, there are three ways to know about a person, three data sources (Cattell & Johnson [1986]) or levels (Leery, 1957) of assessment:
Life data -- From this data source, personality is revealed in everyday behavior, usually reported by someone other than the person being evaluated. Examples are behavioral observations, ratings, school grades, and interview observations.
Question data -- This data source consists of the person's own conscious verbal self-presentation, in a given circumstance. The presentation may be oral, as in an interview, written in essay form, or in responses to multiple-choice questions, as on a personality questionnaire.

Test data -- From this data source, personality is revealed by a person's response to an artificially contrived situation, such as an ability test or a projective test. It is not conscious self-presentation, because the overt task is not self-description. Personality characteristics are inferred from what the person does rather than from direct statements about what kind of person one is. More than from question data, this data source can reveal a person's fantasy projection, as on projective tests.
the 16PF samples a broad base of questions about normal personality style. This broad sampling is, in fact, a distinguishing characteristic of the 16PF. The authors of the 16PF (R. B. Cattell and his collaborators) set out consciously to sample the realm of personality in verbal description. They began with Allport and Odbert's ( 1936) collection of several thousand personal descriptors and reduced it by content analysis to a shorter list. They made rating scales from this smaller number and had fraternity brothers, who might be expected to know each other well, rate one another on all the descriptors. Ratings obtained this way represent an optimum in L-data ratings, averaged over many raters. For example, in any given fraternity, if 30 young men rated each other, any given person's score on a descriptor would be the average among the other 29 fraternity brothers.

The ratings were then submitted to a statistical procedure called factor analysis, the purpose of which is to discover, in a large number of variables, some smaller set that will serve to explain the entire domain. At this point in the research, the factor analysis indicated that 12 variables were enough to account for the domains sampled. From these 12 rating factors (L-data) of personality, the researchers wrote multiple-choice items to represent the domain in a similar way. These questions were tried out on other large groups and the resultant "question data" (Q-data) were factor analyzed, yielding 16 factors of personality. These became the primary factors of the 16PF.

Instruments and Scales
By reason of the items and population involved in its origins, the 16PF is appropriate for persons no younger than 16 years of age. For adolescents and children, two other questionnaires were developed by modifying items from the adult research, trying them out with youngsters of varying ages, and submitting the results to factor analyses. By a series of overlapping studies, two new questionnaires were developed, the HSPQ for youngsters ages 11 to 17 or 18 years, and the CPQ for children ages 8 to 12 years. Thus, the researches of Cattell and his co-workers yielded three linked instruments, with similar scales, over an age span from childhood to full adulthood. At the high end, the 16PF has been used successfully with persons older than 70 years of age. This ability to provide scores on similar variables over a wide age range is, to our knowledge, unique to the 16PF family.

Administration and Scoring
The assessment of personality by questionnaire--the 16PF, HSPQ, or CPQ--involves recording a person's conscious self-presentation in some specific circumstance. One's self-presentation may be expected to change depending on context, on the degree of confidence one has in the person administering the inventory, on the perceived purpose of the results, and so on. For this reason, it is important to establish a comfortable, unambiguous context for the person completing the inventory. Otherwise, the administration instructions are straightforward, and because the questionnaires are untimed, they do not require particularly active supervision. About 80% of persons finish Form A of the 16PF in 40 minutes. Form C, being shorter, is usually completed in half an hour.

Scoring any of the inventories by hand for primary factors only is quick and simple. Raw scores are obtained by placing two grids over the answer sheet and adding points for marked choices, factor by factor. Raw scores are transformed to standard scores (STENS) by a look-up table. For an experienced scorer, the whole process takes 6 or 7 minutes. Getting supplementary scores, secondary factors and others, takes another 5 or 6 minutes for an experienced person.

Computerized scoring is available from the test publisher and from several other licensed sources. Practitioners may mail the answer sheets, access the computer using their own computer by modem, or, in some circumstances, lease scoring software. Computerized scoring services usually provide not only the 16 primary scores but also the secondary factors, as well as derived scores specific to application areas--career counseling, marriage counseling, or clinical diagnosis and treatment.

Reliability

In this section I address three issues that are traditionally called "reliability": stability of scores--how they hold up over time; the internal consistency of the scales--how highly the items in a scale correlate with each other; and interform correlations--the degree to which the various forms of the 16PF, HSPQ, and CPQ seem to measure the same thing.
Stability, Internal Consistency And Interform Correlations
There has been some criticism of the 16PF family of inventories in respect to stability and internal consistency, but in-depth study of the issue has shown that the concerns are based on misunderstandings.

Table 1 presents data (smoothed) from a meta-analysis by Schuerger, Zarrella, and Hotz (1989), which summarized 106 sources and more than eight instruments. Of the studies, 19 involved the 16PF, 5 of them the HSPQ. CPQ data are from the handbook. Values for the second-order factors are from Zarrella (1989). These values are comparable to those for the other instruments, as far as temporal stability is concerned. Internal consistency reliability, taken from a single occasion, unlike temporal stability (test-retest) reliability, is calculated solely from item intercorrelations and the number of items per scale. In this respect, the 16PF has item intercorrelations slightly above average for personality questionnaires, but has relatively few items per scale. It has far fewer items (about 16 per scale) than does the MMPI, for example, which averages about 50 per scale. Because of this small number of items, the internal consistency values for the 16PF and its junior tests are lower than is common among personality questionnaires, except for the second-order values, which compare favorably with those for other instruments.

Table 2 presents averaged correlations among forms and between instruments. They may be compared to two kinds of standards: (a) typical stabilities, as in Table 1, and (b) interform correlations from other instruments. The figures in the table are calculated by correlating the same-named scale across forms or across instruments, as indicated. For example, Factor A-Form A is correlated with Factor A-Form B, Factor B--Form A is correlated with Factor B--Form B, and so on.

The interform and interinstrument correlations presented in the table are all variants of internal consistency reliability, in that they are functions of the correlations among items and the number of items per scale. The relative magnitude of the values in the table illustrates this function. For example, Forms A and B, which have on average about 12 items per scale, show the highest average correlation between similarly named scales.
These figures are close to those found for the straight internal consistency reliability of the instruments presented in the last column of Table 1. They may be compared with those found in other instruments for which alternate forms are available. One example is the correlations found between the Wechsler Adult Intelligence Scale (WAIS) subtests and those on the new WAIS-R, which average .57 (Jackson, 1984). The correlations between corresponding scales on the COP System Interest Inventory (COPS) and the revised COPSR average .72 over 14 subtests (Knapp & Knapp, 1984). In both of these instances the scales purport to measure the same constructs. Correlations from the 16PF family are somewhat lower than are those from the WAIS-WAIS-R comparison, and quite a bit lower than those from the COPS. The differences may be attributed to number of items for the comparison with the WAIS, but not for that with the COPS, which actually has about the same number of items per scale as the 16PF. The practical implication of these correlations is that one usually advises caution in making inferences from a form or instrument based on experience with an alternate form or instrument, except with the second-order factors.
Validity: The 16PF In Career, School, And Clinic

Data On Career And School Application
For both career and school applications, it is convenient to distinguish job or school proficiency from job or school satisfaction. Anticipating a person's job satisfaction from personality information is done by noting the ways a person's characteristics are like those of others persons in various jobs--Holland's "congruence" principle (Holland, 1973). It is the old principle of "like to like." The more similar a person is to others on the job, the more likely the person will feel comfortable. There are, of course, many ways to be dissatisfied with a job, so the principle works only approximately, but it is a useful way to conceptualize fit of a person to a job.
Predicting a person's performance on a job is not the same as predicting a person's satisfaction or comfort with a job. One need only think of persons one knows who are very proficient at a job but uncomfortable with it.

Finding A Job That Fits: Job Satisfaction
To advise a person about fit to an occupation (Holland's congruence principle) one must know what personality profiles characterize various occupations. Much of this kind of information exists for the 16PF in the handbook and elsewhere. For example, DiFiore (1981), Franklin (1983), Nowak (1980), and Anonsen (1985) have all contributed to the understanding of specific occupations in terms of 16PF occupational patterns. Guyer (1984), Johns (1985), and Nasvytis (1988) have treated broader issues of fit to occupation in terms of personality. Some of their efforts are reflected in Table 3 (after Schuerger et al., 1990), which presents average scores for a number of occupations, arranged according to Holland's typology. To apply Holland's principle concretely here, one simply compares the client's score patterns with those of the various known occupational patterns.
The question is best put "In what ways do this client's scores compare with those of the various occupations?" For example, the client in Figure I resembles Realistic and Artistic type occupations in her introversion. She differs from Realistic type occupations in her low self-control, and in this respect is more like Artistic type occupations. Her low Practicality score, in the sensitive direction, puts her more in the artistic group as well. She is unlike those in Enterprising type occupations in most respects but shares the sensitivity with Social types. With Conventional types, she shares introversion and low independence.

This process of comparison might be done by a practitioner and can also be done mathematically by a computer. Results of calculating similarity to the various occupations for large numbers of persons have been encouraging. Among a sample of 1,339 persons representing 21 occupations, approximately 50% of the sample showed their highest similarity to an occupation with a Holland type appropriate to their own current occupation. Counselors will recognize that using only the highest similarity is a very stringent test and that the result compares very favorably with what one usually sees reported for interest measures, for example. Schuerger et al. ( 1990) also reported that similarities, when measured on a small group of graduate students, were very stable over time.

After 8 months, 85% of the students had the identical highest occupational similarity. A total of 93% had as highest either the identical occupation or an occupation within the same Holland type as the Holland type of their prior highest occupational similarity. As many as 7 years later, almost half had the identical highest similarity, and 87% had either identical highest similarity or of same Holland type. In another small sample, of undergraduate psychology majors, the durability of these similarities was tested when students were instructed to try to "look like a personnel officer." Under these conditions, 60% had the identical highest similarity on the second occasion, and 90% were within the same Holland type. Parenthetically, very few managed to increase their similarities to the target occupation, personnel officer.

New Directions
The major need for the 16PF family of instruments is to make validity information available in forms more familiar to clinicians and vocational practitioners. These instruments have seen a great many researches--the 16PF is in the top 10 instruments in this respect, and the HSPQ on its own seems to be in the top 50--but most of the information is not made available in convenient form. That is, for a practitioner, it is useful to know that if a certain scale is over 8, say, and another scale is below 3, then the likelihood of a certain outcome or even of a certain broad description is high. Better yet, that it is 3 out of 5, or some such. To develop such availability, new research is needed, but much can be done with current information.