The items were older than the blank: a thousand of them, written before anyone checked which worked
Hansen's history of the inventory traces the item pool to a seminar Clarence S. Yoakum ran at the Carnegie Institute of Technology in 1919. Its members tried to cover the whole range of human interests, and the pool was written without statistical screening. Several inventories drew on it; Strong's was the one whose method stuck.
Eight parts in 1927. The same eight, reshuffled, in 1938
The Smithsonian lists the 1927 parts in one order and the 1938 Form M in another: school subjects and amusements swap places. Item counts are only published for the 1938 form, and only for four parts.
Build a key, then mark the blank against it
An item enters an occupation's key only if that group's “like” rate differs enough from men in general. The documented example: “making a speech” separated ministers and congressmen from farmers and factory assemblers. Pick a group, set the cut-off, and watch items enter and leave the key.
From 10 occupations to 244 scales
Each column is a form we could date. Bars appear only where a source gives the scale count; click any year for what changed.
Copyrighted 1927 by Stanford; eight parts. Hansen gives 10 occupational scales on the earliest profile.
Sources [1][5]Forester, ad man, teacher, Army classifier, salesmanship researcher — then Stanford
Laid out as the back page of a Strong report form, one row per job he held. Dates follow Darley's 1964 obituary and Hansen's 1987 profile as summarised in secondary sources; “c.” marks approximate spans.
“The motor (abilities) determines how fast the boat can go, the rudder (interests) determines which way the boat goes.”
Strong, Vocational Interests of Men and Women (1943)Interests in his account steer; they do not power. A high engineer score said nothing about whether someone could pass engineering, which is why the 1927 directions open by ruling out intelligence and school work.
For Vocational Interests 18 Years After College (1955) Strong compared the occupations Stanford students later held with the scores they had as students, and argued interest scores stayed stable for decades. His earlier paper on the permanence of interest scores over 22 years (1951) made the same case.
That stability claim is why the blank was used for guidance at all: a score that drifted every few years would be no help choosing a career.
Sources cited on this page
- [1]National Museum of American History. Psychological Test, Vocational Interest Blank (E. K. Strong Jr., © 1927; MA.316371.116).americanhistory.si.eduUsed for: Hero directions quote, 1927 copyright, eight-part list.
- [2]National Museum of American History. Vocational Interest Blank for Men (Revised), Form M (© 1938; 1983.0168.08).americanhistory.si.eduUsed for: 1938 part order, item counts, report columns.
- [3]National Museum of American History. Psychological Test Score Sheets, Strong Vocational Interest Blank (1945).americanhistory.si.eduUsed for: 1945 report forms.
- [4]National Museum of American History. Strong Vocational Interest Blank for Men, Form T399 (1966).americanhistory.si.eduUsed for: 1966 co-authors; revision begun before 1963.
- [5]Hansen, J.-I. C. (1984). The Strong Vocational Interest Blank / Strong-Campbell Interest Inventory. In W. B. Walsh & S. H. Osipow (Eds.), Advances in Vocational Psychology, Vol. 1. Erlbaum.publisher previewUsed for: 1919 seminar and pool, 1921 Carnegie inventory, 10 original scales, early versions, 1985 scale counts.
- [6]Donnay, D. A. C. (1997). E. K. Strong's legacy and beyond: 70 years of the Strong Interest Inventory. Career Development Quarterly, 46(1), 2–22.doiUsed for: Criterion-group method, 1933 women's form, 1974 merger and counts.
- [7]Darley, J. G. (1964). Edward Kellogg Strong Jr., 1884–1963. Journal of Applied Psychology, 48(2), 73–74.read via Wikipedia summaryUsed for: Career dates, Stanford from 1923, dissertations chaired.
- [8]Hansen, J.-I. C. (1987). Edward Kellog Strong Jr.: First author of the Strong Interest Inventory. Journal of Counseling & Development, 66(3), 119–125.read via Wikipedia summaryUsed for: Early life, Forest Service, Columbia, Carnegie, 1926 first interest research.
- [9]Strong, E. K., Jr. (1943). Vocational Interests of Men and Women. Stanford University Press.archive.org searchUsed for: Motor-and-rudder quote; separate forms for women.
- [10]Strong, E. K., Jr. (1955). Vocational Interests 18 Years After College. University of Minnesota Press.archive.org searchUsed for: Follow-up of Stanford students.
- [11]Oxford Reference. Strong Vocational Interest Blank (quick reference entry).oxfordreference.comUsed for: Conflicting 1938 date for the women's form.
- [12]Blackwell, T., & Case, J. (2008). Test review: Strong Interest Inventory, Revised Edition. Rehabilitation Counseling Bulletin, 51(2), 122–126.doiUsed for: 2004 edition item and scale counts.
What changed in this revision
The 1927 blank itself was not read page by page; its structure comes from the Smithsonian's catalogue. No items from any Strong form are reproduced. Strong Interest Inventory is a trademark of The Myers-Briggs Company.
- REMOVEDSpent 14 years building it. No source found for the figure.
- CORRECTED“About 20 occupational scales” in 1927. Hansen gives 10.
- REMOVED“About 400 items.” The 1927 total is reported as 420 only in secondary summaries we could not trace to the blank, so no total is given.
- REMOVED“Millions of students to the 1960s,” “every career inventory since traces back to 1927,” and Holland's Self-Directed Search and Campbell's survey listed as direct descendants. All unsourced.
- ADDEDYoakum item-pool origin, eight-part structure in the 1927 and 1938 orders, edition chart with sourced scale counts, women's form date conflict, Strong's career, and 12 references.
- KEPTThe like/indifferent/dislike blank, now scored against keys built live from criterion-group differences instead of fixed answer patterns.
Related historical tests
The MMPI kept items because criterion groups of patients answered them differently from ordinary people, the same contrast Strong drew between an occupation and men in general. Histories of both instruments link the method directly. It is the best-known clinical use of what began as a career tool.
Strong served on the Army's Committee on Classification of Personnel and taught officers to give Alpha and Beta. Those tests placed recruits by ability alone. His blank, ten years later, added the question the Army never asked: what the man would want to do.
Career counsellors often give the MBTI alongside the Strong, and studies have tested reading the two together. The MBTI sorts people into types from self-report. The Strong instead compares a person with real occupational groups.
Pressey's test also had takers mark long word lists, in his case to show emotional attitudes rather than vocational ones. Both treated a person's pattern of likes and dislikes as data. Pressey scored against expected answers, while Strong scored against groups.
Terman's revision of Binet came out of the same university, measuring the ability Strong's directions say his blank does not measure. Strong called ability the motor and interest the rudder. These two Stanford instruments cover each half.
Modern Strong editions added Personal Style Scales, and research has mapped interest themes onto the five broad personality traits. This page covers that later model. It also includes a short public-domain inventory to try.