Document delivery capabilities of major biomedical libraries in 1968: results of a national survey employing standardized tests.

The standardized Document Delivery Tests (DDT's) developed earlier (Bulletin 56: 241-267, July 1968) were employed to assess the capability of ninety-two medical school libraries for meeting the document needs of biomedical researchers, and the capability of fifteen major resource libraries for filling I-L requests from biomedical libraries. The primary test data are summarized as statistics on the observed availability status of the 300 plus documents in the test samples, and as measures expressing capability as a function of the mean time that would be required for users to obtain test sample documents. A mathematical model is developed in which the virtual capability of a library, as seen by its users, equals the algebraic sum of the basic capability afforded by its holdings; the combined losses attributable to use of its collection, processing, relative inacessibility, and housekeeping problems; and the gain realized by coupling with other resources (I-L borrowing). For a particular library, or group of libraries, empirical values for each of these variables can be calculated easily from the capability measures and the status statistics. Regression equations are derived that provide useful predictions of basic capability from collection size. The most important result of this work is that cost-effectiveness analyses can now be used as practical decision aids in managing a basic library service. A program of periodic surveys and further development of DDT's is recommended as appropriate for the Medical Library Association.