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hindsight bias

the tendency to believe, after learning an outcome, that one would have foreseen it.

critical thinking

thinking that does not blindly accept arguments and conclusions. Rather it examines assumptions, discerns hidden values, evaluates evidence, and assesses conclusions.


an explanation using an integrated set of principles that organizes and predicts observations


a testable prediction, often implied by a theory

operational definition

a statement of the procedures (operations) used to define research variables. (For example, intelligence may be operationally defined as what an intelligence test measures.


repeating the essence of a research study, usually with different participants in different situations, to see whether the basic finding generalizes to other participants and circumstances

case study

an observation technique in which one person is studied in depth in the hope of revealing universal principles


a technique for ascertaining the self-reported attitudes or behaviors of people, usually by questioning a representative, random sample of them

false consensus effect

the tendency to overestimate the extent to which others share our beliefs and behaviors


all the cases in a group, from which samples may be drawn for a study

random sample

a sample that fairly represents a population because each member has an equal chance of inclusion

naturalistic observation

observing and recording behavior in naturally occurring situations trying to manipulate and control the situation

correlation coefficient

a statistical of the extent to which two factors vary together, and thus of how well either factor predicts the others

scatter plot

a graphed cluster of dots, each of which represents the values of two variables.

illusory correlation

the perception of a relationship where none exists


a research method in which an investigator manipulates one or more factors (independent variables) to observe the effect on some behavior or mental process (the dependent variable). By random assignment of participants the experimenter controls other relevant factors


an inert substance or condition that may be administered instead of a presumed active agent, such as a drug, to see if it triggers the effects believed to characterize the active agent

double-blind procedure

an experimental procedure in which both the research participants and the research staff are ignorant (blind) about whether the research participants have received the treatment or a placebo. Commonly used in drug-evaluation studies

placebo effect

an effect on behavior caused by a placebo

experimental condition

the condition of a n experiment that exposes participants to the treatment, that is, to one version of the independent variable

control condition

the condition of an experiment that contrasts with the experimental condition and serves as a comparison for evaluating the effect of the treatment

random assignment

assigning participants to experimental and control conditions by chance, thus minimizing preexisting differences between those assigned to the different groups

independent variable

the experimental factor that is manipulated; the variable whose effect is being studied

dependent variable

the experimental factor-in psychology, the behavior or mental process-that is being measured; the variable that may change in response to manipulations of the independent variable


the most frequently occurring score in a distribution


the arithmetic average of a distribution, obtained by adding the scores and then dividing by the number of scores


the middle score in a distribution; half the scores are above it and half are below it


the difference between the highest and lowest scores in a distribution

standard deviation

a computed measure of how much scores vary around the mean score

statistical significance

a statistical criterion for rejecting the assumption of no differences in a particular study


the enduring behaviors, ideas, attitudes, and traditions shared by a large group of people are transmitted from one generation to the next

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