Validity of the Strong Interest Inventory® Instrument

The Strong Interest Inventory® (Strong) assessment measures career and leisure interests. It is based on the work of E. K. Strong Jr., who originally published his inventory on the measurement of interests in 1927. The assessment is often used to aid people in making educational and career decisions.

The Strong assessment measures interests in four main categories of scales: General Occupational Themes (GOTs), Basic Interest Scales (BISs), Personal Style Scales (PSSs), and Occupational Scales (OSs):

  • 6 GOTs measure basic categories of occupational interests—Realistic, Investigative, Artistic, Social, Enterprising, and Conventional (RIASEC)—based on John Holland’s theory (Holland, 1959).
  • 30 BISs measure clusters of interest related to the GOTs in areas such as Athletics, Science, Performing Arts, and Sales.
  • 5 PSSs—Work Style, Learning Environment, Leadership Style, Risk Taking, and Team Orientation—measure preferences for and comfort levels with styles of living and working. Personal Style Scales were added to the inventory in 1994.
  • 260 Oss (130 for men, 130 for women) measure the extent to which a person’s interests are similar to the interests of people of the same gender working in 130 diverse occupations, such as Accountant, Bartender, and Computer Programmer.

The current norm sample for the Strong is called the General Representative Sample (GRS) and consists of 2,250 individuals (50% men, 50% women). The GRS is generally representative of the racial and ethnic makeup of the U.S. workforce (Donnay, Morris, Schaubhut, & Thompson, 2005). All scales are measured using the GRS, except the OSs (as described above).

Internal consistency reliabilities of all scales are high. GOT reliabilities range from .90 to .95, BISs from .80 to .92, and PSSs from .82 to .87. Determining internal consistency reliability is not appropriate for the OSs because the scales contain items with heterogeneous content and are empirically derived.

Extensive research has demonstrated the validity of the Strong Interest Inventory instrument :

  • Studies have found the GOTs to be predictive of work-related variables (Donnay & Borgen, 1996; Rottinghaus, Lindley, Green & Borgen, 2002).
  • Research has shown the BISs can accurately distinguish occupations (Borgen & Lindley, 2003; Isaacs, Borgen, Donnay & Hansen, 1997; Larson & Borgen, 2002).
  • Validity of the PSSs has been supported through research showing their relationships with the Skills Confidence Inventory (Tuel & Betz, 1998) and MBTI instruments (Hammer & Kummerow, 1996).
  • Validity of the OSs has been demonstrated in research showing their ability to predict the occupations that people will eventually enter (Strong, 1935, 1955; Campbell, 1966; Harmon, 1969; Hansen & Swanson, 1983; Dirk & Hansen, 2004).


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