dependent variablethe variable that gets measured in a research study.descriptive researchresearch methods that involve observing behavior to describe that behavior objectively and systematically.descriptive statisticsdirectionality problemexperimentexperimental groupexperimenter expectancy effectActual change in the behavior of the people or nonhuman animals being observed that is due to expectations of the observerexternal validityhypothesisindependent variablethe variable that gets manipulated in the research study.inferential statisticsinstitutional review boardsinternal validitymeanmedianmeta-analysismodenaturalistic observationA type of descriptive study in which the researcher is a passive observer separated from the situation and making no attempt to change or alter ongoing behavior.negative correlationobserver biasSystematic errors in observation that occur because of an observer's expectations.operational definitiona definition that qualifies (describes) and quantifies (measures) a variable so the variable can be understood objectively.participant observationA type of descriptive study in which the researcher is involved in the situation.populationpositive correlationrandom assignmentreactivityThe phenomenon that occurs when knowledge that one is being observed alters the behavior being observed. Hawthorne effect.reliabilityreplicationresearchsamplescatterplotscientific methodselection biasself-report biasself-report methodsMethods of data collection in which people are asked to provide information about themselves such as in surveys or questionnaires.standard deviationtheorythird variable problemvariabilityvariablesomething in the world that can vary and that a researcher can manipulate, measure or both.zero correlation