{"id":14859,"date":"2021-03-01T11:10:38","date_gmt":"2021-03-01T10:10:38","guid":{"rendered":"https:\/\/www.scribbr.com\/?p=14859"},"modified":"2023-06-22T10:30:34","modified_gmt":"2023-06-22T08:30:34","slug":"control-variable","status":"publish","type":"post","link":"https:\/\/www.scribbr.com\/methodology\/control-variable\/","title":{"rendered":"Control Variables | What Are They & Why Do They Matter?"},"content":{"rendered":"

A control variable<\/strong> is anything that is held constant or limited in a research study. It\u2019s a variable that is not of interest to the study\u2019s objectives<\/a>, but is controlled because it could influence the outcomes.<\/p>\n

Variables may be controlled directly by holding them constant throughout a study (e.g., by controlling the room temperature in an experiment), or they may be controlled indirectly through methods like randomization<\/a> or statistical control (e.g., to account for participant characteristics like age in statistical tests). Control variables can help prevent research biases<\/a> like omitted variable bias<\/a> from affecting your results.<\/p>\n

\"Control<\/a><\/p>\n\n\n\n\n\n\n\n
Examples of control variables<\/caption>\n
Research question<\/th>\nControl variables<\/th>\n<\/tr>\n<\/thead>\n
Does soil quality affect plant growth?<\/td>\n\n
    \n
  • Temperature<\/li>\n
  • Amount of light<\/li>\n
  • Amount of water<\/li>\n<\/ul>\n<\/td>\n<\/tr>\n
Does caffeine improve memory recall?<\/td>\n\n
    \n
  • Participant age<\/li>\n
  • Noise in the environment<\/li>\n
  • Type of memory test<\/li>\n<\/ul>\n<\/td>\n<\/tr>\n
Do people with a fear of spiders perceive spider images faster than other people?<\/td>\n\n