The second important concept is inference. An inference is an “informed leap” from the observed or measured value to an estimate of some underlying variable. This is called an inferential leap because we cannot directly observe what is being measured, but we can observe its manifestations. Through observation of the results of the measurement process, an inference can be made about the underlying characteristics and its nature or status.
Short and long inferential leaps are possible. For a long time, writing tests were multiple choice tests of grammar, usage, vocabulary, and mechanics, (long inferential leap). Writing assessments have changed to be a shorter inferential leap of student writing ability by actually asking a student to produce writing samples. Long or short, the leap still exists. The scenario of producing a writing sample is contrived–a more realistic measure of a student’s writing ability is when students write for their own purposes. We probably feel more comfortable with shorter inferential leaps. However, longer inferential leaps may be preferred by policymakers for cost reasons; it is cheaper to do the proxy measure, the more distal inference, than to do the shorter inferential leap in many cases.