Research is a methodical process of identifying a research topic, obtaining a representative sample, identifying a reliable method, collecting data, and analyzing the results. Some aspects of a study cannot be controlled. For example, the researcher may not be able to control how many persons participate or the attrition rate. When the results of a study could have been affected by events or occurrences that could not be controlled, these are identified as limitations to the study. All studies have limitations, regardless of diligent planning by researchers. When evaluating a study, one must weigh the success of the researcher’s efforts to ensure reliability and validity of results obtained against the limitations.