Define psychological assessment. In your answer, discuss and show full knowledge of the following concepts: assessment tools, clinical interview, psychological testing, reliability, and validity.

Psychological assessment refers to the systematic gathering and evaluation of information pertaining to an individual for whom a specific question about psychological functioning needs answering. Assessment requires the clinician to place and interpret scores and other data within the context of the person's history, referral information, behavioural observations and life story of that person in order to provide a comprehensive understanding of that individual. Assessment can be carried out with a wide variety of techniques, typically including a clinical interview and a number of psychological tests. If relevant to the referral question, biological assessments (e.g., EEG, brain imaging techniques) may be required. Issues of reliability and validity pertain to each of the assessment tools selected. Specific issues of reliability and validity pertain to specific tools - for example unstructured clinical interviews are often needed in order to establish trust and rapport, but this tool has problems of reliability and validity stemming from the subjectivity and bias that may be present, such as when the clinician's initial assumptions about the problem guide her questions and other questions - that would shed light on important aspects of the situation - are left out.