**3. Validity aspects of frailty scales and indicators used in elderly population**

Much as reliability may be loosely assumed to be synonymous to precision in measurements, it follows a natural pattern then to ensure validity by the assumption of accuracy. It must be understood that geriatrics, just as other branches of clinical medicine, is essentially an applied science field. To this end, the reader is cautioned against making substantial error in reasoning, that of assuming measurement exactness of constructs made in its clinical measurements, just as natural scientists make, in say reaction time in subjects like physics or chemistry. It is on this basis, that all aspects of validity, discussed in this chapter, constitute a number of assumptions, some of them may be hard to prove, even when considered useful in the stated models. For instance, since most validation processes in constructing frailty scales and indicators consisted of a number of items, the assumptions made are such that those items, when taken collectively, refer to a construct of frailty, and that when applied to humans in their contextual nature, can distinguish those who are frail from those who are not. This section will deal with one important form of validity measurement, that of construct validity at most [41].

Construct validity is a way of measuring a disposition/character/trait/belief such that its accuracy can be estimated with quantifiable degrees of confidence. In simplistic fashion, it is a way of measuring a test for what it claims to quantify. Construct validity differs from other forms of validity in applied sciences, namely, criterion and content validity, since in construct validation, there is an aspect of quantifying the quality of a measuring instrument toward what it claims to measure. Thus, for all practical purposes, this chapter will endeavor to quantify aspects hypothesized to assess frailty, as applied to the community of senior citizens living in different geographical communities. This notion, inter alia, follows the appreciable level of acceptance in reliability indices prior to its undertaking, lest of that, it may be deemed invalid in practice. In this sub-section, an analysis of different frailty scales/indicators in construct validity will be determined here underneath.
