The determination of whether learning has taken place depends upon what questions are asked and how they are asked. Regardless of the subject or grade level, there is an infinity of indicators that can provide information about the action or subject under consideration. The precision of the measurement depends on the means used to gather data and the extent to which data are collected. To put it another way, a meaningful evaluation depends largely upon the quality of the indicators utilized. Frequently, several different indicators may be considered.
Statistics can easily determine the correlations among indicators.
By knowing the capacity of the indicators to assess the subject and the correlation between various indicators, it is possible to form inferences from one indicator to another. If the indicators are highly correlated, then it is no longer a question of which is better, but which is more cost effective. For example, if the eighth grade TCAP language arts achievement test is highly correlated with the eighth grade writing assessment, then it is not necessary to use both from an evaluation perspective. Both may be needed for other reasons, e.g., the test results for calculating gains and the writing assessment as part of an instructional strategy. Absolute accuracy in any type of measurement is impossible.