Determination of fluid category 2. Water in fluid category 1 whose aesthetic quality is impaired owing to: 1  a change in its temperature; or. 2  the presence of substances or organisms causing a change in its taste, odour or appearance, including water in a hot water distribution system.
Credibility is defined as the quality or power of inspiring belief. Credible sources, therefore, must be reliable sources that provide information that one can believe to be true. It is important to use credible sources in an academic research paper because your audience will expect you to have backed up your assertions with credible evidence.
Internal validity. In scientific research, internal validity is the extent to which a causal conclusion based on a study is warranted, which is determined by the degree to which a study minimizes systematic error (or 'bias'). It contrasts with external validity, the degree to which it is warranted to generalize results to other contexts.