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hindsight bias

the tendency to believe, after learning an outcome, that one would have foreseen it. (Also known as the I-knew-it-all-along phenomenon)

overconfidence

the tendency to be more confident than correct, to overestimate the accuracy of one's beliefs and judgments

critical thinking

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

theory

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

hypothesis

a testable prediction, often implied by a theory

operational definition

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

replication

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

case study

research method that involves an intensive investigation of one or more subjects in hopes of revealing universal principles

survey

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

population

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 without trying to manipulate and control the situation

stratified random sample

a sample from selected subgroups of the target population in which everyone in those subgroups has an equal chance of being included in the research

correlation coefficient

a statistical measure of the extent to which two factors vary together, and thus of how well either factor predicts the other; ranges from -1 to +1

scatterplot

a graphed cluster of dots, each of which represents the values of two variables. The slope of the points suggests the direction of the relationship between the two variables. The amount of scatter suggests the strength of the correlation (little scatter indicates high correlation). (Also called a scattergram or scatter diagram.)

positive correlation

A correlation where as one variable increases, the other also increases, or as one decreases so does the other. Both variables move in the same direction.

negative correlation

the relationship between two variables in which one variable increases as the other variable decreases

illusory correlation

the perception of a relationship where none exists

experiment

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 aims to control other relevant factors.

placebo

experimental results caused by expectations alone; any effect on behavior caused by the administration of an inert substance or condition, which the recipient assumes is an active agent.

placebo effect

experimental results caused by expectations alone; any effect on behavior caused by the administration of an inert substance or condition, which is assumed to be an 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

experimental condition

the condition of an 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 that is being measured; the variable that may change in response to manipulations of the independent variable

descriptive research

has the purpose of observing and recording behavior; case studies, surveys, and naturalistic observations

correlational research

the study of the natural relationship between two variables such that systematic changes in the value of one variable are accompanied by systematic changes in the other; allowing us to predict the value of one variable from the other

mode

the most frequently occurring score in a distribution

mean

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

median

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

range

the difference between the highest and lowest scores in a distribution

standard deviation

a measure of variability that describes an average distance of every score from the mean

statistical significance

a calculation central to inferential statistics that describes the likelihood that the results of a study happened by chance

normal curve

the symmetrical bell-shaped curve that describes the distribution of many physical and psychological attributes; most scores fall near the average, and fewer and fewer scores lie near the extremes

z-score

standard score indicating the number of standard deviations above or below the mean

culture

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