Reliability+and+Validity

= Reliability and Validity  = The definition of **reliability** is "the extent to which an assessment yields consistent information about the knowledge, skills, or characteristics being assessed" (Ormrod 2011). In other words, if students perform at the same rate and obtain the same results from an assessment, the assessment is considered reliable.

There are three different types of reliability:
 * 1) **Test - Retest Reliability**: whether or not an assessment produces the same results over a short period of time
 * 2) **Scorer Reliability**: whether or not different people agree on the judgment of the performance produced
 * 3) **Internal Consistency Reliability**: whether or not multiple parts of the assessment can measure a single characteristic of the assessment

Reliability can also be affected by various factors in the classroom setting. Teachers must keep these variables in mind when assessing the performance of their students and whether or not the results they obtain are reliable. If students experience any form of change, such as rearrangement of the classroom, the administration of the assessment, changes in the type of assessment or simple day-to-day changes, the results of an assessment may not be reliable. The reliability may also hinder on factors affecting the teacher as well, such as mood, environment and other outside variables (Ormrod 2011).

The definition of **validity** is "the extent to which an assessment actually measures what it is intended to measure and allows appropriate inferences about the characteristic or ability in question" (Ormrod 2011). Therefore, a valid assessment it one in which we can ensure students have understood the task given.

There are three different types of validity are as follows:
 * 1) **Content Validity**: used typically for summative assessments to gauge overall knowledge
 * 2) **Predictive** **Validity**: indicates future performance in a particular domain
 * 3) **Construct Validity**: the assessment measures abstract and/or unobservable characteristics

Within the construct of the classroom, validity is most important. In using a valid assessment, educators can correctly conclude what a students' knowledge level is on a particular subject area. For example, a paper quiz or test might be able to tell whether or not a student can memorize content, something that can be deemed as reliable. However, this method cannot validly assess whether or not a student can apply what they have learned to a real-life situation.

The diagram below gives a visual explanation of validity and reliability and how it pertains to shooting an arrow:

Sources: Ormrod, Jeanne E. (2011). //Educational Psychology: Developing Learners, Seventh Edition.// Boston, Pearson. p. 511 - 521.

Image: http://explorable.com/images/validity-and-reliability.jpg

Page Developed by: Jacqueline Daur, October 2013.