When using a source, it is important to determine its reliability and validity. In other words, is the source believable? Is the data current and reliable, or too outdated? Is it biased, and therefore, unreliable? This resource will help students learn how to evaluate each source based on its origin, purpose, value, and limitation (OPVL). A chart that may be used as a poster or handout, along with an OPVL template is included.