Critical thinkingArticle: Oosterveld & Vorst 2010Testconstructie en testonderzoek There are problematic theories about validityExamples van viewpoints Dorsboom (2003) According to Dorsboom, it is plausible that the mercury thermometer is a valid measurement of temperature of objects, because differences in the real temperature cause differences in the measurement-instrument.If the causal string is described exactly, and this is a plausible representation of reality, than is the instrument valid in reality.Real validity is unknown as long as not all the relevant knowledge is available.Because it is in principle unknown in what extent relevant knowledge is available, validity is hypothetical unsure.Even if the causal string between true variation in the trait and the measured variation is known well, knowledge about the causal strings can change due to new knowledge. This is why real validity is hypothetical.However, people can have a judgment about the validity of measurement-instruments. This validity-judgment doesn’t have anything to do with the real validity.In psychology, true causal strings are (yet) impossibleThat is why psychology temporarily deals with hypothetical validity-judgments. This is in suspense of more precise and true causal strings between true trait-variation and measurement-variation.The quality of measurement, not the validity, must be proven from psycho-metrical analysis (reliability, one-dimensionality, representative content of the measurement-instrument, connections with external criteria, support of theoretical expected connections)Science-philosophical viewpointIf a test is valid...