INTEREST INVENTORIES - Central University Library, …cachescan.bcub.ro/e-book/E1/580683/203-215.pdf · INTEREST INVENTORIES ... est and Skill Survey TM, the Career Assessment

CHAPTER 9

INTEREST INVENTORIES

Jo-lda C. Hansen, Ph.D.

INTRODUCTION

The study of interests and the development of interest inventories emerged from applied psy- chology. The importance of an individual's interests in job selection was first recognized by edu- cators in the 1900s and shortly thereafter by industry. Early theorists in the field, such as Par- sons (1909), hypothesized that occupational adjustment was enhanced if an individual's characteristics and interests matched the requirements of the occupation. As E. K. Strong, Jr. (1943) pointed out in Vocational Interests of Men and Women, interests provide additional information, not available from analyses of abilities or apti- tudes, for making career decisions. Consideration of interests, along with abilities, values, and personality characteristics, provides a thorough eval- uation of an individual that is superior to consideration of any trait in isolation.

The earliest method for assessing interests was estimation, accomplished by asking individuals to indicate how they felt about various activities. To improve on the accuracy of their estimation, people were encouraged to try out activities before making their estimates. However, try-out tech- niques for evaluating interests were time consum- ing and costly; the search for a more economical assessment method led to development of interest checklists and rating scales (Kitson, 1925; Miner, 1922) and eventually to interest inventories that used statistical procedures to summarize an individual's responses to a series of items representing various activities and occupations.

The Earliest Item Pool

The first item pool of interest activities was accumulated in a seminar taught by Clarence S. Yoakum at Carnegie Institute of Technology in 1919. The 1,000-item pool was developed using a rational sampling approach designed to represent the entire domain of interests. Over the years, statistical analyses were performed to determine the worth of each item, and numerous test authors used that original item pool as the foundation for development of their inventories (e.g., Occupational Interest Inventory [Freyd, 1922-1923], Interest Report Blank [Cowdery, 1926]; General Interest Survey [Kornhauser, 1927]; Vocational Interest Blank [Strong, 1927]; Purdue Interest Report [Remmers, 1929]; Interest Analysis Blank [Hub- bard, 1930]; Minnesota Interest Inventory [Pater- son, Elliott, Anderson, Toops, & Heidbreder, 1930]).

Characteristics of Good Items

Interest inventory items should be evaluated periodically because societal changes can make items obsolete as well as create the need for new items. Several qualities that contribute to the excellence of items, and ultimately to the excellence of an interest inventory, can be used to assess the value of each item.

First, items should differentiate among groups because the purpose of interest inventories is to distinguish people with similar interests from those with dissimilar interests. The item in Figure 9.1,

203

2 0 4 HANDBOOK OF PSYCHOLOGICAL ASSESSMENT

Examples of Hish,est Samples

91% Ministers 89% U.S. Congress Members 84% State Legislators 82% Governors 80% Salespeople 77% Chamber of Commerce Executives 76% Sales Managers

Examp, l.e.s of Lowest Samples

9% Farmers 9% Factory Assemblers I0% Sewing Machine Operators 11% Carpenters 11% Beauticians 11% Telephone Operators 12% Lab Technicians

251

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10 20 30 40 50 60 70 80 90 100--

Percent "Like" Response

Number

of

Samples

Figure 9.1. Percent "Like" responses to the item Making a speech for 350 occupational samples.

for example, has the power to spread 350 occupations over a wide range of response percentages. The lowest "Like" response rate for this item, Making a Speech, is 9 percent (meaning that few people in the sample answered "Like" to the item), and response rates range up to a high of 91 percent (meaning that the majority of the sample responded "Like").

Samples or groups with similar interests should have similar item-response rates, and clusters of groups with high or low response rates should make sense. In Figure 9.1, for example, the samples of ministers, members of the U.S. Congress, state legislators, governors, salespeople, and Chamber of Commerce executives had high "Like" response rates of 77-91 percent. Farmers, factory assemblers, sewing machine operators, carpenters, beauticians, and laboratory technicians, however, had low "Like" response rates to the same item. Those clusters of high and low response-rate samples are intuitively satisfying and illustrate the item's con-

tent validity; one expects ministers and politicians, for example, to enjoy making a speech.

Items also should be sex-fair; no item should suggest that any occupation or activity is more appropriate for one sex than the other. In addition to sex-fair items, all interpretive and instructional materials for interest inventories should be sex-fair.

To facilitate adaptation of inventories for use with ethnic minorities or for international use, interest items should be unambiguous and cul- ture-fair. Straightforward items also are more likely to have the same meaning for everyone taking the inventory regardless of cultural or occupational orientation, and they will be easier to translate into several languages.

All items should be revised periodically to ensure that they are current and familiar to the respondents. The face validity, as well as content validity, of an interest inventory is affected if the item pool contains obsolete items that are unfamiliar to the general population. On the other hand, as

INTEREST INVENTORIES 205

new technologies develop, new items should be generated to ensure that the entire domain of interests is represented in the item pool.

Finally, items should be easy to read. All materials that accompany interest inventories (e.g., instructions, profile, interpretive information) and the item pool itself should be easy to read to make the inventory useful for a wide educational and age- range in the population.

Theories of Vocational Interests

The earliest interest inventories were developed using the atheoretical, empirical method of contrast groups that is based on an assumption that people with similar interests can be clustered together and, at the same time, be differentiated from groups with dissimilar interests. Inventories that still incorporate this method of scale construction are the Strong Interest Inventory 1 (Harmon, Hansen, Borgen & Hammer, 1994), the Career Assessment Inventory TM2 (Johansson, 1975" 1986) and the Campbell Interest and Skill Survey TM (CISS(R~3; Campbell, Hyne, & Nilsen, 1992).

Results from the early empirical investigations of interests later were used to develop hypotheses about the structure of interests. Anne Roe (1956) and John Holland (1959), for example, used the factor analysis of Guilford and his colleagues (Guilford, Christensen, Bond, & Sutton, 1954), who found seven interest factors: (a) mechanical, (b) scientific, (c) social welfare, (d) aesthetic expression, (e) clerical, (f) business, and (g) out- door work, to guide the development of their theories about interests.

CONSTRUCTION OF INTEREST INVENTORY SCALES

Construction of interest inventories is based on several assumptions:

1. First, a person can give informed responses of degree of interest (e.g., like, indifferent, dislike) to familiar activities and occupations.

2. Then, unfamiliar activities have the same factor structure as do familiar activities.

3. Therefore, familiar activities and occupations can be used as items in interest inventories to identify unfamiliar occupational interests.

Early interest inventories typically featured either homogeneous or heterogeneous scales. Now, however, many inventoriesmCampbell Interest and Skill Survey TM, the Career Assessment Inventory TM, the Kuder Occupational Interest Sur- vey (KOIS) (Form DD) (Kuder, 1966), and the Strong Interest Inventory--combine homogeneous and heterogeneous scales. Generally, heterogeneous scales are more valid for predictive uses of interest inventories (e.g., predicting future job entry or college major), but homogeneous scales are more useful for providing parsimonious descriptions of the structure of a sample' s interests (Edwards & Whitey, 1972).

Homogeneous Scale Development

One method of scale construction involves clus- tering together items based on internal consistency or homogeneous scaling. Items chosen in this man- ner have high intercorrelations. Empirical methods, such as cluster or factor analyses, can be used to identify the related items. The scales of the Vocational Interest Inventory (VII) (Lunneborg, 1976), for example, were constructed using factor analysis. The scales also may be based on rational selection of items; this method uses a theory to determine items appropriate for measuring the construct represented by each scale. For example, the General Occupational Themes of the Strong Interest Inventory were rationally constructed using Holland's theoretical definition of the six vocational types to guide item selection (Campbell & Holland, 1972; Hansen & Johansson, 1972).

Heterogeneous Scale Development

The Occupational Scales of the Campbell Inter- est and Skill Survey TM, the Career Assessment Inventory TM, Strong Interest InventoryVM 1, and the Kuder Occupational Interest Survey (Form DD) are composed of items with low intercorrelations, and therefore, are called heterogeneous scales. Heterogeneous scales are atheoretical: in other words, the choice of items is based on empirical results rather than an underlying theory. The CISS (R~, the Career Assessment Inventory TM, and the Strong Interest Inventory use TM the empirical method of contrast groups to select items; this technique compares the item-response rates of occupational criterion groups and contrast groups,

206 HANDBOOK OF PSYCHOLOGICAL ASSESSMENT

representing the interests of people in general, to identify items that significantly differentiate the two samples. The KOIS uses a different empirical method that compares an individual's item- response pattern directly to the item-response pat- terns of criterion samples that represent the interests of various occupations and college majors.

CURRENT INTEREST INVENTORIES

One of the most recently developed interest inventories is the Campbell Interest and Skill Sur- vey TM (Campbell, 1995). Other widely used inventories include the Vocational Preference Inventory (Holland, 1985c), the Self-Directed Search (SDS) (Holland, 1971, 1987a, 1994), various forms of the Kuder, the Strong Interest Inventory TM, the Career Assessment Inventory TM, the Jackson Vocational Interest Survey (JVIS) (Jackson, 1977), the unisex version of American College Testing's Interest Inventory (UNIACT) (Lamb & Prediger, 1981; Swaney, 1995), and the Vocational Interest Inven- tory (VII) (Lunneborg, 1976).

Campbell Interest and Skill Survey

David Campbell, author of the Campbell Interest and Skill Survey TM (CISS (R), describes the instrument as a product of 90 years of psychometric evo- lution influenced to a large extent by Campbell's work with the Strong Interest Inventory TM in the 1960s, 1970s and 1980s (Campbell, 1995). The CISS (R) is unique among interest inventories in that the instrument is designed to assess not only an individual's interest in academic and occupational topics but also an individual's estimation of her or his skill in a wide range of occupational activities. The profile includes 98 scales on which two scores are provided--an interest score and a skill score.

Item Pool and Profile

The item pool for the CISS (R) includes 200 interest items and 120 items designed to assess self- reported skills. The response format for the interest items is a six-point scale ranging from "Strongly Like" to "Strongly Dislike". The skill items also have a six-point response scale that includes self evaluations of Expert, Good, Slightly Above Aver-

age, Slightly Below Average, Poor, and None (have no skills in this area).

5cales

The CISS (R) profile includes three types of scales: seven Orientation Scales, 29 Basic Scales, and 60 Occupational Scales. The Orientation Scales capture the major interest factors that have been identified through various statistical cluster- ing procedures and include Influencing (business and politics), Organizing (managing and attention to detail), Helping (service and teaching), Creating (the arts and design), Analyzing (science and math), Producing (hands-on and mechanical), and Adventuring (physical activities and competition). The Orientation Scales are used as the organizational frame of reference for the CISS (R) profile (see Figures 9.2 and 9.3).

The 29 Basic Scales were developed by cluster- ing together homogeneous items in content areas such as Sales, Supervision, Adult Development, International Activities, Science, Woodworking, and Military/Law Enforcement. These scales are grouped on the profile under the Orientation with which they correlate most highly (see Figure 9.2).

The Occupational Scales were constructed using the empirical method of contrast groups originally refined for interest measurement by E. K. Strong, Jr. Successful, satisfied workers in each of 60 occupations were surveyed. Their responses to each of the CISS (R) items were compared to the item responses of a general reference sample composed of employed workers from a variety of occupations. Items that substantially differentiated the occupational criterion sample from the general reference sample were selected for the occupation's scale.

The first step to determine the location of the Occupational Scales on the profile, was to compute the mean score for each occupational criterion sample on the Orientation Scales. The occupation's highest Orientation score then was used to locate the Occupational Scale on the profile. For example, the test pilot and ski instructor criterion samples scored highest on the Adventuring Orien- tation, and therefore, the Occupational Scales representing their interests are clustered with the Adventuring Orientation on the profile (see Figure 9.3).

Two additional scales on the CISS (R) profile are Academic Focus and Extraversion. The Aca-


CAMPBELL INTEREST AND SKILL SURVEY INDIVIDUAL PROFILE REPORT

CLIENT FAUX [

Orientations lmw me and Basic Scales ~1~ ~ 30

Influencin

Orientations andBasic Scales [ Very Low Low Mid-Range High

35 40 45 50 55 60

DATE SCORED: 11106195

Very High Interest/Skill • 65 70 Pattern

Law/Politics

Public Speaking

Sales

Advertising/Marketing . .

Financial Services

Office Practices

Adult Development

Counseling

Child Development

Religious Activities

Medical Practice

Performing Arts

Writing

International Activities

Fashion

Culinary Arts

Mathematics

Science

Mechanical Crafts

Woodworking

Farming/Forestry

Plants/Gardens

Animal Care

Athletics/Physical Fitness

Military/Law Enforcement

Risks/Adventure

Figure 9.2. Profile for the Orientations and Basic Scales for the CISS Ira. Copyright © 1988, 1992 David P. Campbell, Ph.D. All rights reserved. Used here by permission.


CAMPBELL INTEREST AND SKILL SURVEY INDIVIDUAL PROFILE REPORT

CLIENT FAUX [

ii l u l l U I O r i e n t a t i o n Sca l e

Adventuring Orientation' I DATE SCORED: 11/06/95 ii ii i iii i

... O c c u p a t i o n a l Sca le s I ! Otiea-- * VctyLow Low Mid-i~al, Hilt, Ve~jHigh l t t t ~ l l t~ttOnco~ ~st~a25 30 35 40 45 50 55 60 65 70 75

* Ve~ Low Low Mid4~mle Hilh Vay Hi~ ** StL.tdard lnmrut/$kill S c o t ~ 3 0 35 40 45 50 55 60 65 70 Pattern

Adventuring[ I 4 7 ~ ~ 1 ~ : .... ~ 4P

Bas i c In te res t and Ski l l Sca l e s I

Very Low Low Mid-I~lle Hi|h V ILl ~ 3 0 35 40 45 50 55 60 7 ~ 7 0

Phys. Fitness i ~ M i l i ~ / ~51 . . . .

...... L a w El ' if . 3 4 3 ~ t ~ : !~( i i l i Avoid

Adventure 50 .........

Police Officer ,

Military Officer

Ski Instructor .....

Test Pilot

Athletic Coach

Athletic Trainer ,,,

Emergency Medical tecnmcmn

Fitness Instructor

i i

The Adventuring Orientation focuses on athletic, police, and military activities involving physical endurance, risk taking, and teamwork. People who score high are robust and vigorous, enjoying both physical challenges and competitive outlets. Adventurers are active, energetic, and confident in strenuous or dangerous situations. They also enjoy the opportunity to work with others in skilled, disciplined groups such as athletic teams or military units. Typical high-scoring individuals include military officers, police officers, athletic coaches, emergency medical technicians, and fitness instructors.

Your Adventuring interest score is mid-range and your skill score is low. People who have this pattern of scores typically report moderate interest but little confidence in physically active, adventurous, and competitive activities, such as athletics, police work, and military activities.

Your scores on the Adventuring Basic Scales, which provide more detail about your interests and skills in this area, are reported above on the left-hand side of the page. Your scores on the Adventuring Occupational Scales, which show how your pattern of interests and skills compares with those of people employed in Adventuring occupations, are reported above on the right-hand side of the page. Each occupation has a one-, two-, or three-letter code that indicates its highest Orientation score(s). The more similar the Orientation code is to your highest Orientation scores (which are reported on page 2), the more likely it is that you will find satisfaction working in that occupation.

lUUll u HI * Standard Scores: I (0) = Interests; S (0) = Skills

** Interest/Skill Pattern: Pursue = High Interests, High Skills; Develop = High Interest, Lower Skills; Explore = High Skills, Lower Interests; Avoid = Low Interest, Low Skills

*** Orientation Code: l = influencing; O= Organizing; H= Helping; C= .O'eating; N=aNalyzing; P= Producing; A = Adventuring I" ' , Range of middle 50%o of people in the occupation: Solid Bar .= Interests; Hollow Bar = Skills

Figure 9.3. Profile for the Adventuring Orientation of the CISS. Copyright © 1988, 1992 David P. Campbell, Ph.D. All rights reserved. Used here by permission.


demic Focus Scale measures interest and confidence in academic pursuits especially science and the arts. The Extraversion Scale measures interest and confidence in activities that require high levels of personal interaction.

area if the interest score is high but the skill score is low, to Explore the area if interest is low and skill high, or to Avoid if both interest and skill scores are low.

Validity and Reliability

Norming and Profile Report

All of the scales on the CISS (R) are normed on a general reference sample of women and men. The scales also are standardized with the result that the mean score for the general reference sample is about 50 and the standard deviation about 10. The sample used to norm the scales included 1,790 female and 3,435 male respondents from 65 occupational samples. The raw score means for the two samples were averaged to give the sexes equal weighting in the raw-score-to-standard-score conversion.

The CISS (R~ Report is an l l -page document that includes one page that reports the Orienta- tion and Basic Scale Interest and Skills scores as illustrated in Figure 9.2. An additional seven pages summarize scores for all of the scales related to each of the seven Orienta- tions as illustrated in Figure 9.3 for the Adven- turing Orientation. The additional three pages include one page for the special scales and procedural checks, and finally, a two page summary.

In addition to presenting an interest and a skill score for each scale, the profile also includes a graph that plots the interest and skill scores to provide interpretive comments ranging from very low to very high. An interpretive bar representing the middle 50 percent of scores for each criterion sample on its own Interest and Skill scales also is provided on the profile (solid bar = Interests; hollow bar = Skills) for the Occupational Scales. Finally, each of the seven Orientation pages includes a short interpretive report that summarizes the individual's results.

Measurement of both interests and confidence in skills enriches the interpretive information that can be gleaned from the CISS (R~ scores. Based on a comparison of the level of the interest and skills scores for each scale, the individual is advised to Pursue the area if both the interest and skill scores are high, to Develop the

Substantial evidence of the construct validity of the interest and skill scales is presented in the manual of the CISS (R) (Campbell, Hyne, & Nilsen, 1992). Test-retest correlations over a 90-day interval are .87, .83, and .87 for the Orientation, Basic, and Occupational interest scales, respectively, and .81, .79, and .79 for the Orientation, Basic, and Occupational skill scales.

Holland's Interest Inventories

Emergence of John Holland's theory of careers (Holland, 1959, 1966, 1992) began with the development of the Vocational Preference Inventory (VPI) (Holland, 1958). Based on interest data col- lected with the VPI as well as data from other interest, personality, and values inventories and from analyses of the structure of interests, Holland for- mulated his theory of vocational life and personality. According to Holland, people can be divided into six types or some combination of six types: Realistic, Investigative, Artistic, Social, Enterpris- ing, and Conventional. Holland indicates that the types can be organized in the shape of a hexagon in the R-I-A-S-E-C order; the types adjacent to one another on the hexagon (e.g., Realistic-Investiga- tive or Enterprising-Conventional) are more related than types that are diametrically opposed to one another (e.g., Realistic-Social or Artistic-Con- ventional). Attempts to verify Holland' s hexagonal representation of the world of work show, in general, that the structure of interests approximates the theoretical organization proposed by Holland (Campbell & Hansen, 1981; Cole & Hanson, 1971; Hansen, Collins, Swanson, & Fouad, 1993; Haverkamp, Collins & Hansen, 1994; Prediger, 1982; Rounds, 1995).

Holland' s theory has led to development of inventories and sets of scales to measure his six types, for example, his own Self-Directed Search, the ACT Interest Inventory, the Career Decision-Making Sys- tem-Revised (CDM-R) (Harrington & O'Shea, 1993), the General Occupational Themes of the Strong Interest Inventory TM (Campbell & Holland, 1972;


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Figure 9.4. Profile for the Vocational Preference Inventory. Reproduced and adapted by special permission of the Publisher, Psychological Assessment Resources, Inc., Odessa, FL 33556, from the Vocational

Preference Inventory by Dr. John L. Holland, Ph.D., Copyright 1978, 1985 by PAR, Inc. Further reproduction is prohibited without permission from PAR, Inc.

INTEREST INVENTORIES 21 1

How To Organize Your Answers

Start on page 4. Count how many times you said L for "Like." Record the number of L's or Y's for each group of Activities, Competencies, or Occupations on the lines below.

ActivtUes (pp. 4-5) ~ _ _ (P ~ ' ~ ~ _ _ 4~) R I A S E C

Competencies (pp. 6-7) q 8 J A0 x ~, R I A S E C

o ~ . w U o ~ (p. 8) Z (B dO ~ • 0 R I A S E C

Self-Estimates (p. 9, 6 ~" ;~ 6 ~[ q (What number did) R I A S E C you circle?)

c, _¢_ ,/ ¥ R I A S E C

Total Scores (Add the five R scores, the five I scores, the five A scores, etc.) ~ , ~ ' 3 ~ ~ ~ ~ , ~ , / I ~

R I A S E

Iq C

The letters with the three highest numbers indicate your summary code. Write your summary code below. (If two scores are the same or tied, put both letters in the same box.)

Summary Code

Highest 2nd 3rd

Figure 9.5. Summary code and scores for the SDS. Adapted and reproduced by special permission of the Publisher, Psychological Assessment Resources, Inc., Odessa, FL 33556, from the Self-Directed Search Assessment

Booklet by John L. Holland, Ph.D. Copyright 1970, 1977, 1985, 1990, 1994 by PAR, Inc. Further reproduction is prohibited without permission from PAR, Inc.


Hansen & Johansson, 1972), and the General Themes of the Career Assessment Inventory TM.

Vocational Preference Inventory

Development of the Vocational Preference Inventory (VPI) was based on a series of theoretical and empirical reports. Holland surveyed personality, vocational choice, and vocational interest literature; identified interest-personality factors; and hypothesized how they related to one another. Then, he used 160 occupational titles to develop an item pool that represented the interest factors or types.

The current version of the VPI (Holland, 1985c) has seven homogeneous scales, constructed in a series of rational-empirical steps that measure Self-Control (Sc) plus the six types hypothesized in Holland's theory: Realistic (R), Investigative (I), Artistic (A), Social (S), Enterprising (E), and Conventional (C). Other VPI scales developed using empirical methods of scale construction include: Acquiescence (Ac), measuring willing- ness to say "yes" to items; Status (St), indicating interest in occupational status; Masculinity-Femi- ninity (Mf), measuring interest in occupations tra- ditionally preferred by men or women; and Infrequency (Inf), assessing the tendency to answer items in an atypical direction.

The VPI may be hand scored; raw scores are plotted either on the female profile shown in Fig- ure 9.4 or a male profile. Even though Holland is a strong proponent of the use of raw scores for predicting occupational membership, the profile is calibrated to provide standard scores based on either 378 female or 354 male college students and employed adults to provide comparisons across scales.

Self-Directed Search

The Self-Directed Search (SDS) (Holland, 1985b, 1987a, 1994), similar to the VPI, was developed to measure Holland's six types. It may be self-administered, self-scored, and to a limited degree, self-interpreted. The 228-item assessment booklet includes four sections: Activities the respondent would like to do; Competencies; Occu- pations; and Self-Estimates.

The reading level of the SDS is estimated to be at the seventh- or eighth-grade level; Form Easy

(E), which has only 203 items, is rated at the fourth-grade level. As illustrated in Figure 9.5, the most important feature of the SDS profile is the summary codes. The three highest raw scores represent the respondent's primary, secondary, and tertiary code assignments. Holland (1979) suggests flexibility in using the three summary codes for occupational exploration, since the codes are approximate, not precise

A series of materials has been developed to assist in the interpretation of the SDS. The 1987 Manual Supplement (Holland, 1987a) explains the use of the SDS in individual- and group-career assistance. The Occupations Finder (Holland, 1985a) and The College Majors Finder (Holland, 1987b) provide three-letter Holland codes for 1,156 occupations and more than 900 college majors, respectively. Occupational and educational alter- natives can be identified by surveying the two booklets to find possibilities with summary codes which are similar to the individual's summary code.

Reliability and Validity. The median test-retest reliability coefficient for the 11 VPI scales over a two-week interval is .72; over the same period the median reliability coefficient for the six SDS scales is .82 for high school students and over 7 to 10 months, .92 for college students (Holland, 1978, 1979, 1985b, 1985c). Studies of the predictive validity of the VPI and SDS, for choice of occupation and college major over one-, two-, and three-year intervals, range from 35 percent to 66 percent accuracy (Holland, 1962, 1979, 1985c, 1987a; Hol- land & Lutz, 1968).

Strong Interest Inventory

The earliest version of the Strong Vocational Interest Blank (R~4 (1927) used the empirical method of contrast groups to construct occupational scales representing the interests of men in 10 occupations. The first form for women was published in 1933, and until 1974 the instrument was published with separate forms for women and men. In 1974 (Campbell, 1974), the two forms were combined by selecting the 325 best items from the previous women's (TW398) and men's (T399) forms and in 1981 (Campbell & Hansen, 1981) another revision was completed in an effort to provide matched-sex Occupational Scales (e.g., male- and female-normed Forester Scales, male- and


female-normed Flight Attendant Scales, male- and female-normed Personnel Director Scales). The 1985 revision (Hansen & Campbell, 1985) marked the end of the sex-equalization process which began in 1971. One additional major change in the 1985 revision was the expansion of the breadth of the profile to include more nonprofessional and vocational/technical occupational scales. The most recent revision of the Strong was completed in 1994 (Harmon, Hansen, Borgen, & Hammer, 1994).

equal to 50 and standard deviation of 10 (see Figure 9.6).

For most occupations, matched-sex scales are presented on the Strong Interest Inventory profile. However, seven of the 109 occupations (211 Scales) are represented by just one scale (e.g., f Child Care Provider, f Dental Assistant, f Dental Hygienist, f Home Economics Teacher, f Secre- tary, m Agribusiness Manager, and m Plumber).

General Occupational Themes

Item Pool and Profile

The item booklet for the 1994 revision of the Strong Interest Inventory includes 317 items, divided into eight sections: Part 1, Occupational Titles; Part 2, School Subjects; Part 3, Activi- ties; Part 4, Leisure Activities; Part 5, Types of People; Part 6, Forced-choice Preference Between Two Activities; Part 7, Self-Descrip- tion Characteristics, and Part 8, Preference in the World of Work. The item format requires respondents to indicate the degree of their interest in each item by responding "Like," "Indiffer- ent," or "Dislike."

The profile includes four sets of scales: six Gen- eral Occupational Themes, 25 Basic Interest Scales, 211 Occupational Scales that represent pro- fessional and nonprofessional occupations (e.g., farmers, geographers, photographers, social workers, buyers, credit managers), and four Personal Styles Scales.

Occupational Scales

The Occupational Scales of the Strong are another example of test construction using the empirical method of contrast groups. The response-rate percentage of the occupational criterion sample to each item is compared to the response-rate percentage of the appropriate-sex contrast sample (i.e., General Reference Sam- ple of females or males) to identify items that differentiate the two samples. Usually 30 to 50 items are identified as the interests ("Likes") or the aversions ("Dislikes") of each occupational criterion sample. The raw scores for an individual scored on the Occupational Scales are con- verted to standard scores based on the occupational criterion sample, with mean set

The General Occupational Themes (GOT) are a merger of Strong's empiricism with Holland' s theory of vocational types. The six homogeneous Themes contain items selected to represent Hol- land's definition of each typemRealistic, Investi- gative, Artistic, Social, Enterprising, and Conventional. Data comparing the enhanced 1994 GOT to Holland's Vocational Preference Inven- tory or Self-Directed Search are not available. However, the 1985 GOT correlated highly (.72 to .79) with same-named Vocational Preference Inventory scales (Hansen, 1983). Correlations between the GOT indicate that the hexagonal order that Holland proposes to describe the relationship between his types (adjacent types have more in common than do diametrically opposed types) also describes the relationship between the Strong Interest Inventory Themes (Harmon et al., 1994).

Figure 9.7 illustrates the score information provided for the General Occupational Themes on the profile; the same information is presented for the Basic Interest Scales. The standard scores are based on a General Reference Sample composed of women and men with mean set equal to 50 and standard deviation of 10. In addition to standard scores, interpretive bars provide a visual representation of the dis- tribution of the female General Reference Sam- ple (upper bar) and male General Reference Sample (lower bar), respectively.

The integration of Holland's theory with Strong's empiricism provides the organizational framework for the current Strong profile. The Occupational Scales are coded with one to three Holland types based on the criterion sample's highest scores on the General Occupational Themes. The codes, in turn, are used to categorize the Occupational Scales on the profile (see Figure 9.6). The Basic Interest Scales (BIS) also are clustered according to Holland types by identifying the

214 H A N D B O O K OF PSYCHOLOGICAL ASSESSMENT

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Figure 9.6. Profile for the General Occupational Themes and the Basic Interest Scales of the Strong. Modified and reproduced by special permission of the Publisher, Consulting Psychologists Press, Inc., Palo Alto, CA 94303 from the Strong Interest Inventory TM of the Strong Vocational Interest Blanks ~RI Form T317. Copyright 1933, 1938, 1945, 1946, 1966, 1968, 1974, 1981,1985, 1994 by The Board of Trustees of the Leland Stanford Junior University. All rights reserved. Printed under license from Stanford University Press, Stanford, CA 94305. Further reproduction is prohibited without the Publisher's written consent. Strong Interest Inventory is a trademark and Strong Vocational Interest Blanks is a registered trademark of the Stanford University Press.


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Figure 9.7. Profile for the Realistic and Investigative Occupational Scales of the Strong. Modified and reproduced by special permission of the Publisher, Consulting Psychologists Press, Inc., Palo Alto, CA 94303 from the Strong Interest Inventory TM of the Strong Vocational Interest Blanks ~R~ Form T317. Copyright 1933, 1938, 1945, 1946, 1966, 1968, 1974, 1981, 1985, 1994 by The Board of Trustees of the Leland Stanford Junior University. All rights reserved. Printed under license from Stanford University Press, Stanford, CA 94305. Further reproduction is prohibited without the Publisher's written consent. Strong Interest Inventory is a trademark and Strong Vocational Interest Blanks is a registered trademark of the Stanford University Press.

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