Page 111 - A Step-By-Step Guide to Questionnaire Validation Research

alluded to earlier, a latent variable such as quality of life,

compliance and depression cannot be objectively

measured by using any machine or device. The best way

to measure these latent variables is to develop a reliable

and valid questionnaire for measuring them. Some

examples of the commonly-used questionnaires that

measure latent variables include CDI (measure depression

symptoms among children), SF-36 (measure quality of life),

SDSCA (measure diabetes self-care activities), DASS

(measure psychological symptoms) etc. and all these

questionnaires have already been validated through an

assessment of their construct validity (Kovacs, 1992; Ware

& Sherbourne, 1992; Toobert & Glasgow, 1994; Lovibond

& Lovibond, 1995).

The construct validity measures both convergent

and discriminant validity at the same time. Convergent

validity refers to the degree to which the scores obtained