Student Resources Study Guides and Tips The Random Selection Experiment Method By Kendra Cherry Kendra Cherry Facebook Twitter Kendra Cherry, MS, is the author of the "Everything Psychology Book (2nd Edition)" and has written thousands of articles on diverse psychology topics. Kendra holds a Master of Science degree in education from Boise State University with a primary research interest in educational psychology and a Bachelor of Science in psychology from Idaho State University with additional coursework in substance use and case management. Learn about our editorial process Updated on November 27, 2020 Fact checked Verywell Mind content is rigorously reviewed by a team of qualified and experienced fact checkers. Fact checkers review articles for factual accuracy, relevance, and timeliness. We rely on the most current and reputable sources, which are cited in the text and listed at the bottom of each article. Content is fact checked after it has been edited and before publication. Learn more. by Emily Swaim Fact checked by Emily Swaim LinkedIn Emily is a board-certified science editor who has worked with top digital publishing brands like Voices for Biodiversity, Study.com, GoodTherapy, Vox, and Verywell. Learn about our editorial process Print Rob Friedman / Getty Images When researchers need to select a representative sample from a larger population, they often utilize a method known as random selection. In this selection process, each member of a group stands an equal chance of being chosen as a participant in the study. Random Selection vs. Random Assignment How does random selection differ from random assignment? Random selection refers to how the sample is drawn from the population as a whole, while random assignment refers to how the participants are then assigned to either the experimental or control groups. It is possible to have both random selection and random assignment in an experiment. Imagine that you use random selection to draw 500 people from a population to participate in your study. You then use random assignment to assign 250 of your participants to a control group (the group that does not receive the treatment or independent variable) and you assign 250 of the participants to the experimental group (the group that receives the treatment or independent variable). Why do researchers utilize random selection? The purpose is to increase the generalizability of the results. By drawing a random sample from a larger population, the goal is that the sample will be representative of the larger group and less likely to be subject to bias. Factors Involved Imagine that a researcher is selecting people to participate in a study. In order to pick participants, they might choose people using a technique that is the statistical equivalent of a coin toss. They might begin by using random selection to pick geographic regions from which to draw participants. They might then use the same selection process to pick cities, neighborhoods, households, age ranges, and individual participants. Another important thing to remember is that larger samples tend to be more representative because even random selection can lead to a biased or limited sample if the sample size is small. When the sample size is small, an unusual participant can have an undue influence over the sample as a whole. Using a much larger sample size tends to dilute the effects of unusual participants and prevent them from skewing the results. The Experimental Group In Psychology Experiments 1 Source Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Lin L. Bias caused by sampling error in meta-analysis with small sample sizes. PLoS ONE. 2018;13(9):e0204056. doi:10.1371/journal.pone.0204056 Additional Reading Elmes DG, Kantowitz BH, Roediger HL. Research Methods in Psychology. Belmont, CA: Wadsworth; 2012. By Kendra Cherry Kendra Cherry, MS, is the author of the "Everything Psychology Book (2nd Edition)" and has written thousands of articles on diverse psychology topics. Kendra holds a Master of Science degree in education from Boise State University with a primary research interest in educational psychology and a Bachelor of Science in psychology from Idaho State University with additional coursework in substance use and case management. See Our Editorial Process Meet Our Review Board Share Feedback Was this page helpful? Thanks for your feedback! What is your feedback? Other Helpful Report an Error Submit