Content validity is a statement about the content of a variable, that is to say the aspects that are part of or should be part of to the meaning of a construct.
The origin of content validity
Validity can be viewed as a rating score that lies between 0 and 100, in which 0 means that it is not at all clear what is meant and 100 means that there is no doubt about the meaning of what is being measured. To make a good rating you can take a closer look at two aspects: content validity and construct validity. In this section we will discuss content validity. Elsewhere we discuss construct validity.
Suppose you want to do a research in which ‘satisfaction with the place to live’ is an important issue. There are several ways to measure this, for instance: Give a rating score for how satisfied you are with the place you live:………
This gives a rather raw score.
If you want to have a more finetuned score you should ask more question. For instance:Give on a 5-point rating scale how happy you are with …
… the living room
… the doorway
… the kitchen
… the sleeping room
… the bathroom
Now you might think that this gives a nice and good view about how satisfied a person is with the house he is living in. Would you give it a rate of 100? Well, maybe some aspects are missing. Should not the garden be an aspect too? Or contact with the neighbours? And maybe aspects of the way the local government takes care of the neighbourhood is an important issue of satisfaction with the place to live.
And now, what is content validity?
Content validity is raising and answering the question if all aspects that are part of a construct are measured. You can try to give the answer yourself, but it is better to contact some experts in the field of research. Ask them if your test or questionnaire is complete. Also talk with some of the people in your target group. Ask some of them to fill in the questionnaire and afterwards ask if they think the questionnaire is complete and if they could answer all the questions. That is the way to find out if some aspects are missing.
Afterwards, that is after gathering the data, you can check if all items are part of the same construct by applying a factor analysis. That topic is discussed elsewhere on this site.
Tip: Make use of existing questionnaires and tests. Then you don’t have to argue about content validity. If everyone else is measuring a construct in a particular, already standardised way, then why should you be so wise to do it differently? You must have good reasons for it.>
Related topics to content validity:
- Construct validity
- Predictive validity
- Face validity
- Internal validity
- External validity
- Factor analysis
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- Testing instruments with factor analysis and Cronbachs alpha