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Instrument Triangulation and Adaptation
By Daniel R. Zalles, Ph.D.

It is assumed that by this point in your evaluation project, you have determined your evaluation questions, from whom you want to collect data, whether to collect the data from an entire population of interest or from a sample, and what sample size you desire. This module focuses on the adaptation of existing instruments, not on their development (see modules on specific types of instruments for development strategies).

Instrument triangulation is the concurrent or near-concurrent administration of multiple instruments about the same phenomena. Its aims are achieved when different information gathered with different instruments provides evidence that supports a common interpretation or conclusion. An example would be gathering data about a common set of teachers' skills through a combination of teacher questionnaires, teacher interviews, principal interviews, classroom observations, student interviews, student test scores, examination of tasks assigned by the teacher to the student, and examination of student work products. Instrument triangulation is advisable when no single source of information provides a definitive answer to an evaluation question (e.g., each of the various sources of information provides potentially incomplete, fragmentary, or biased, information); therefore, it is necessary to gather corroborative and complementary information.

The main benefit of instrument triangulation is that it can sharpen the clarity of results, strengthen the validity of findings, and enhance the credibility of conclusions. However, even if warranted, instrument triangulation is often expensive. Therefore, you may need to carefully consider the costs and benefits of instrument triangulation for your particular evaluation question. When evaluating a course of study, for example, it might be appropriate to triangulate a student learning assessment with a questionnaire that asks the students to describe what they learned in the course. On the other hand, when background information about the demographics of a school district is needed, it might be sufficient to simply obtain the information, if available, from state archives. This module is written for evaluations in which the use of instrument triangulation would be prudent.

This module envisions a three-step process. Step 1 describes how to conceptualize an instrument triangulation strategy. Step 2 describes how to search for and adapt such instruments. And Step 3 describes how to institute quality control of instruments through editing and piloting before the instruments are used in data collection.

The objectives of this module are that you understand the following:

  • What benefits accrue from triangulating information sources with the use of multiple instruments
  • How to make methodical, comprehensive, and efficient decisions about which instruments to use and to whom those instruments should be administered.