Functionally interest inventories are closely related to the aptitude tests since their main use is in vocational and educational guidance. An important advantage of the standardized inventory over the interview is the possibility of comparing responses of those of reference groups.
There are three approaches to inventory construction are:
1. Empirical Keying:
The Strong blank (Strong vocational interest blank SVIB) this was first published in 1927. It has been developed by means of a strictly empirical procedure i.e. it makes very few psychological assumptions and develops scoring formulas entirely on the basis of observed correlation is of responses with criteria.
The Kuder preference record, on the other hand, describes the individual in terms of psychological traits. The strong inventory is comparable to the aptitude test designed for a particular occupation, where trial-and-error selection of items maximizes predictive power and theory of ability plays little part in the test construction. The Kuder inventory is more comparable to multi score aptitude tests intended to describe distinct aspects of ability; the practical implications of such abilities remain to be established after the test is developed.
The SVIB consists of questions on hundreds of activities both vocational and a vocational. Most of the 400 items require a “like-indifferent- dislike” response to activities or topics: biology, fishing, being an aviator, planning a sales campaign, etc. Strong tried to select activities that adolescents would know or be able to imagine, rather than activities that become meaningful only as a result of work experience.
2. Homogeneous Keying: The Kuder Preference Record:
The evolution of Kuder’s inventory was almost exactly opposite to that of Strong’s. Kuder began with a factor analysis of single items in order to identify clusters of interests, and then organized these items into descriptive scales. The scales were used in educational and vocational guidance even though predictions rested on inference rather than evidence of predictive validity.
However, today scores for specific occupations can be constructed from the Kuder profile although the instrument is still used most often as a trait description. Kuder identified ten clusters of occupational interests (a cluster being a group of items which have substantial correlationis with each other. Such a group is said to be homogeneous, i.
e., there is a common factor running through the items). The ten scores constituting the Kuder profile are : outdoor, mechanical, computational, scientific, persuasive, artistic, literary, musical, social service, and clerical. Each item is in the “forced- choice” form.
Three activities are listed out of which one is to be selected. The occupational interpretation is usually made by identifying the two highest scores in the profile referring to a list of occupations for which those scores are believed or known to be relevant.
3. Logical Keying: The Lee-Thorpe Inventory:
This is the third approach to questionnaire construction.
The interest inventory by Lee and Thorpe is a set of questions selected and organized on the basis of judgement rather than on statistical grounds. This is referred to as the “Logical” approach and contrasts with the ones discussed before. It is similar to the technique of constructing proficiency tests by defining a universe of situations and selecting items randomly from that universe. The Lee-Thorpe inventory consists of 120 items having preferences in couplets and additional 33 having preferences in triplets.
It measures interest in six occupational fields business, arts, natural, personal social and sciences.