Replication: repetition of an experiment to confirm the results. Theory: a model of interconnected ideas and concepts that explains what is observed and makes predictions about future events. Hypothesis: a specific prediction of what should be observed in the world if a theory is correct. Research: scientific process that involves the systematic and careful collection of data. Variable: something in the world that can be measured and that can vary. Operational definition: the quantification of a variable that allows it to be measured. Experiment: a study that tests casual hypotheses by measuring and manipulating variables. Independent variable: in an experiment, the condition that is manipulated by the experimenter to examine its impact on the dependent variable. Dependent variable: in an experiment, the measure that is affected by manipulation of the independent variable. Confound: anything that affects a dependent variable that may unintentionally vary between the different experimental conditions of a study.