Feedback on their performance

on correct answer) may be a further source of test unreliability. 
C. Validity 
By far the most complex criterion of an effective test-and arguably the most important 
principle-is validity, “the extent to which inferences made from assessment result are 
appropriate, meaningful, and useful in terms of the purpose of the assessment” (Ground, 
1998, p. 226). A valid test of reading ability actually measures reading ability-not 20/20 
vision, nor previous knowledge in a subject, nor some other variable of questionable 
relevance. To measure writing ability, one might ask students to write as many words as 
they can in 15 minutes, then simply count the words for the final score. Such a test would 
be easy to administer (practical), and the scoring quite dependable (reliable). But it would