CHARACTERISTICS OF RESEARCH TOOLS:

An ideal measuring instrument is one which results  in measures that are relevant, accurate objective, sensitive and  efficient. Measures which are physical or physiological have a higher chance of success  in  attaining these goals than measures that are psychological and behavioural. A number of  techniques have been developed  to evaluate the quality of the measuring tool to minimize error. You  have already read about the characteristics  of standardize evaluation tool. However when you construct a tool or select a tool you must ensure the following characteristics: 

i) Validity 

Refers to the degree  to which  the  tool measures, what  it  is  intended  to measure. It refers  to whether the instrument or scale is quantifying what it claims  to  e.g. weight 'scale measures body weight and it  is valid; a tool which is valid  for one measure, need  not  be valid for another e.g.  in  the case of weighing scale: it is not valid  to measure  temperature.