Im talking about tests not designed for self-administration like the moca,wais etc. Could the scored potentially be deflated or inflated and misadministered thus making them invalid?
There are quite a few factors to consider when taking an assessment. For one, the external conditions of your environment, and your internal mindset should ideally be standardised.
An example of external standardised conditions are a consistent room temperature, a quite space to take the test, or an external examiner to check that no one cheats.
Internally, the test taker should not be hungry, and should understand the test instructions, for example.
By taking the test yourself, the conditions will likely not meet this criteria of standardisation necessary for the results to be comparable. If you want to know a bit more, there are norm-referenced, and criterion-referenced assessments. The first kind compare your scores to the scores of other test takers, like a pub quiz, for example; scores are compared, and the team with the most points wins. Here, if the conditions are not standardised, your results will not be comparable to others.
Criterion-referenced measures compare your score to a predetermined benchmark, like an exam at school; if you score above 50%, you pass. In this case, a lack of standardised conditions means you may not answer the questions as intended, and so the benchmark comparison will also lose meaning.
C. Foxcroft & G. Roodt. (2001). Introduction to psychological assessment in the South African context.