I am conducting a qualitative study which i need to develop a scale, I need to know how to assess the reliability and validity of this scale?
ArE you doing something like an exploratory sequential mixed methods design (qual --> QUANT) where the goal of the qualitative study is to develop the content for a survey?
If, so you can only assess reliability and validity once you collect the survey data. In particular, both reliability and validity require assessing correlations between pre-specified combinations of variables, but the goal of your qualitative study is to create such variables, not measure them.
Dear Prof David,
Thank you very much for you response, I will be grateful If you suggest methods for assessing the reliability and validity, Cronbach alpha alone is good or another thing also can be used?
Cronbach's alpha is widely accepted, and I don't know of any other reliability coefficient that even comes close to it in acceptance.
Validity is a more complex topic than reliability, and I recommend you search for information about "construct validity."
Dear Hamdan
According to Churchill (1979), Cronbach's Alpha is the first measure used to assess the instrument quality. Hair et al. (2010) defend that anything above .7 indicates satisfactory reliability. Additionally, you should calculate composite reliability. CR offers better estimates of the shared variance amongst the items. You can use SPSS or other statistics software to calculate. If you need a more detailed information on developing questionnaires check Hinkin (1998) and Koufteros (1999).
Good luck in your research!
Best Regards
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