Errors in test results: The “quick guide” part 2

In the last edition of Assessment News (Part 1 of this “quick guide”), we looked at how measurement error limits the precision of test scores. In this edition of Assessment News we examine how another source of error—sampling error—affects how we can use test results for a group. For example, we need to consider sampling error if we want to use the test results to make judgements about the general effectiveness of the teaching and learning programme the group was involved in.