Statistics for People Who (Think They) Hate Statistics

by Neil J. Salkind

the equivalence or similarity between two different forms of the same test. For example, let’s say that you are doing a study on memory and part of the task is to look at 10 different words, memorize them as best you can, and then recite them back after 20 seconds of study and 10 seconds of rest. Because this study takes place over a 2-day period and involves some training of memory skills, you want to have another set of items that is exactly similar in task demands, but it obviously cannot be the same as far as content. So, you create another list of words that is hopefully similar to the first. In this example, you want the consistency to be high across forms—the same ideas are being tested, just using a different form. Measurement people think of the larger pool of items that could be used as one big “test,” so by comparing forms, they are looking at the relationship of a test with itself. All types of reliability do that—look at the relationship between a test and itself.