Page 29 - A Step-By-Step Guide to Questionnaire Validation Research

variance, or the degree to which variables “move” together

(Tabachnick & Fidell, 2001).

Measures of quality of life (QoL), depression and

satisfaction are some common examples of latent

variables. Furthermore, a broad domain such as QoL can

be subdivided into several sub-domains that measure

specific aspects of QoL, such as physical aspects of QoL,

emotional aspects of QoL, family aspects of QoL, and so

on, all of which are considered latent variables. At least

two questions or items are needed to adequately measure

a domain of interest and some research studies may

require at least ten (or more) questions to measure a

specific domain of interest (The DCCT Research Group,

1988; Toobert & Glasgow, 1994).

In order to measure a specific latent variable by

using a questionnaire, the researcher will need to develop

a study instrument or a questionnaire to measure the