validity

• Internal validity


  Refers to the test or measure being used, for example, in an experiment, whether changes in the DV are caused by the IV rather than sources of error. For self-reports, we can consider this problem in several ways
• Face validity


  Whether a measure appears, at face value, to test what it
• Criterion validity


  Indicates whether a phenomenon measured in one way will relate to, or predict, some other related variable. This relationship can indicate what will happen in the future, and is correct in this forecast
• Concurrent validity


  A type of criterion validity, whether a measure will produce a similar score for a particular individual as another test that claims to assess the same phenomenon. This can be assessed by comparing the results to a measure known to be effective
• Construct validity


  A wider idea, looking at whether a measure is based on some certain-to-exist phenomenon, which it tests. It arises as a consequence of combined theoretical and empirical research, rather than being the product of a single measure or procedure
• External validity


  Relates to issues beyond the investigation, particularly whether the findings will generalise to other populations, location, contexts and times than the ones investigated. This includes the concept of ecological validity
• Population validity


  The extent to which findings from one sample can be generalised to the whole of the population from which the sample was taken, and to other populations. Many factors affect whether such generalisations can be made, such as the sampling method used, the size of the sample, the narrowness (or otherwise) of the sample and the nature of the phenomenon being tested
• If the sample is deemed to be representative, ie. to have the range of relevant characteristics that are found in the wider population, then the findings should generalise from the sample to that population. So, to achieve representativeness, the sample tested should include a good cross section of the population, so that all the different categories of people within in it are included