Truth and Evidence in Validity Theory

According to Kane (this issue), “the validity of a proposed interpretation or use depends on how well the evidence supports” the claims being made. Because truth and evidence are distinct, this means that the validity of a test score interpretation could be high even though the interpretation is false. As an illustration, we discuss the case of phlogiston measurement as it existed in the 18th century. At face value, Kane's theory would seem to imply that interpretations of phlogiston measurement were valid in the 18th century (because the evidence for them was strong), even though amounts of phlogiston do not exist and hence cannot be measured. We suggest that this neglects an important aspect of validity and suggest various ways in which Kane's theory could meet this challenge.