The Fog Index, Flesch Reading Ease, Flesch-Kincaid readability formula and Gunning-Fog Index are formulas that have also been used to determine readability in validity.Major drawback of content validity is that it is also adjudged to be highly subjective like face validity.This is called a translational or representational validity.

Several varieties have been described, including face validity, construct validity, content validity and criterion validity (which could be concurrent and predictive validity).

These validity tests are categorised into two broad components namely; internal and external validities. It is the mostly used data collection instrument in health and social science research.

It could be adapted from an already tested one or could be developed as a new data tool specific to measure or quantify a particular attribute.

These conditions therefore warrant the need to test validity and reliability of questionnaire.

Face validity is often said to be very casual, soft and many researchers do not consider this as an active measure of validity.

For example, a researcher is interested in evaluating employees' attitudes towards a training program on hazard prevention within an organisation.

However, in some cases, researchers could combine more than one form of validity to increase validity strength of the questionnaire.

For instance, face validity has been combined with content validity Its major disadvantage is that such predictor may not be available or easy to establish.

He wants to ensure that the questions (in the questionnaire) fully represent the domain of attitudes towards the occupational hazard prevention.

The development of a content valid instrument is typically achieved by a rational analysis of the instrument by raters (experts) familiar with the construct of interest or experts on the research subject.

One of the most common tasks often encountered in social science research is ascertaining the validity and reliability of a measurement tool. As simple as this may seems, it is often omitted or just mentioned passively in the research proposal or report.