independent groups design an experimental design in which different groups of participants are exposed to independent Variable dependent Variable conditions control variable control group treatment group placebo group confounds systematic variability unsystematic variability selection effect random assignment matched group design between groups design within groups design posttest only design pretest posttest design concurrent measures design repeated measure design power carryover effects practice effects order effects counterbalancing manipulations check variable that is manipulated in the experiment in regression analysis it is the variable used to explain variance in the criterion variable the variable that is measured or the outcome variable in regression analysis the single outcome or criterion variable one of the levels of the independent variable in an experiment a potential variable that an experimenter holds constant on purpose a level of an independent variable that is intended to represent no treatment or a neutral condition the participants in an experiment who are exposed to the level of the independent variable that involves a drug therapy or intervention a control group that is exposed to an inert treatment a potential alternative explanation for a research finding threat to internal validity in an experiment the situation that occurs when the levels of a variable coincide in some predictable way with experimental group membership creating a potential confound in an experiment the situation that occurs when the levels of a variable coincide in some predictable way with experimental group membership creating a potential confound a threat to internal validity that occurs when the kinds of participants at one level of the independent variable are systematically different from those at the other level of the independent variable the use of a random method to assign participants into different experimental groups experimental design in which participants who are similar on some measurable variable are grouped into sets and the members of each matched set are then randomly assigned to different experimental conditions different levels of the independent variable such that each participant experiences only one level of the independent variable same as independent groups design a study design in which each participant is presented with all levels of the independent variable an experiment with an independent groups ensign in which participants are tested on the dependent variable only once an experiment with an independent groups design in which participants are tested on the key dependent variable twice once before and once after exposure to the independent variable an experiment using a within groups design in which participants are exposed to all the levels of an independent variable at roughly the same time and a single attitudinal or behavioral preference is the dependent variable an experiment with a within groups design in which participants respond to a dependent variable more than once after exposure to each level of the independent variable the probability that a study all show a statistically significant result when some effect is truly present in the population a threat to internal validity that occurs when being exposed to one condition changes how people react to a later conditions a type of order effect in which peoples performance improves overtime because they became practiced at the dependent measure a threat to internal validity that occurs when being exposed to one condition changes how people react to a later conditions presenting the levels of the independent variable to participants in different orders to control the order effect an extra dependent variable that researchers can include in an experiment to determine how well an experimental manipulation worked pilot study a study completed before or sometimes after the study of primary interest usually to test the effectiveness or characteristics of the manipulations