Parallel forms refer to different versions of a test or assessment that measure the same underlying construct or ability. These forms are designed to be equivalent in terms of difficulty and content, allowing for reliable comparisons of scores. This approach is often used in educational settings to evaluate student progress without the risk of memorization affecting results. In psychological testing, parallel forms can help ensure that the assessment is fair and unbiased. For example, if a researcher uses two parallel forms of the Wechsler Adult Intelligence Scale, they can administer one form at the beginning of a study and the other later, providing a more accurate measure of changes in intelligence over time.