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.) (Myers Psychology for AP 2e p. 031)
critical thinking
thinking that does not blindly accept arguments and conclusions. Rather, it examines assumptions, assesses the source, discerns hidden values, evaluates evidence, and assesses conclusions. (Myers Psychology for AP 2e p. 035)
theory
an explanation using an integrated set of principles that organizes observations and predicts behaviors or events. (Myers Psychology for AP 2e p. 038)
hypothesis
a testable prediction, often implied by a theory. (Myers Psychology for AP 2e p. 038)
operational definition
a carefully worded statement of the exact procedures (operations) used in a research study. For example, human intelligence may be operationally defined as what an intelligence test measures. (Myers Psychology for AP 2e p. 039)
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. (Myers Psychology for AP 2e p. 039)
case study
a descriptive technique in which one individual or group is studied in depth in the hope of revealing universal principles. (Myers Psychology for AP 2e p. 040)
naturalistic observation
observing and recording behavior in naturally occurring situations without trying to manipulate and control the situation. (Myers Psychology for AP 2e p. 040)
survey
a technique for ascertaining the self-reported attitudes or behaviors of a particular group, usually by questioning a representative, random sample of the group. (Myers Psychology for AP 2e p. 042)
sampling bias
a flawed sampling process that produces an unrepresentative sample. (Myers Psychology for AP 2e p. 043)
population
all those in a group being studied, from which samples may be drawn. (Note: Except for national studies, this does not refer to a country's whole population.) (Myers Psychology for AP 2e p. 043)
random sample
a sample that fairly represents a population because each member has an equal chance of inclusion. (Myers Psychology for AP 2e p. 043)
correlation
a measure of the extent to which two variables change together, and thus of how well either variable predicts the other. (Myers Psychology for AP 2e p. 046)
correlation coefficient
a statistical index of the relationship between two variables (from -1 to +1). (Myers Psychology for AP 2e p. 046)
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). (Myers Psychology for AP 2e p. 046)
illusory correlation
the perception of a relationship where none exists. (Myers Psychology for AP 2e p. 050)
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 variables. (Myers Psychology for AP 2e p. 051)
experimental group
in an experiment, the group exposed to the treatment, that is, to one version of the independent variable. (Myers Psychology for AP 2e p. 051)
control group
in an experiment, the group not exposed to the treatment; contrasts with the experimental group and serves as a comparison for evaluating the effect of the treatment. (Myers Psychology for AP 2e p. 051)
random assignment
assigning participants to experimental and control groups by chance, thus minimizing preexisting differences between the different groups. (Myers Psychology for AP 2e p. 051)
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. (Myers Psychology for AP 2e p. 051)
independent variable
the experimental factor that is manipulated; the variable whose effect is being studied. (Myers Psychology for AP 2e p. 052)
confounding variable
a factor other than the independent variable that might produce an effect in an experiment. (Myers Psychology for AP 2e p. 052)
dependent variable
the outcome factor; the variable that may change in response to manipulations of the independent variable. (Myers Psychology for AP 2e p. 052)
validity
the extent to which a test measures or predicts what it is supposed to. (See also content validity and predictive validity.) (Myers Psychology for AP 2e pp. 053, 622)
descriptive statistics
numerical data used to measure and describe characteristics of groups. Includes measures of central tendency and measures of variation. (Myers Psychology for AP 2e p. 057)
histogram
a bar graph depicting a frequency distribution. (Myers Psychology for AP 2e p. 057)
mode
the most frequently occurring score(s) in a distribution. (Myers Psychology for AP 2e p. 057)
mean
the arithmetic average of a distribution, obtained by adding the scores and then dividing by the number of scores. (Myers Psychology for AP 2e p. 057)
median
the middle score in a distribution; half the scores are above it and half are below it. (Myers Psychology for AP 2e p. 057)
skewed distribution
a representation of scores that lack symmetry around their average value. (Myers Psychology for AP 2e p. 058)
range
the difference between the highest and lowest scores in a distribution. (Myers Psychology for AP 2e p. 058)
standard deviation
a computed measure of how much scores vary around the mean score. (Myers Psychology for AP 2e p. 058)
normal curve (normal distribution)
a symmetrical, bell-shaped curve that describes the distribution of many types of data; most scores fall near the mean (about 68 percent fall within one standard deviation of it) and fewer and fewer near the extremes. (Myers Psychology for AP 2e pp. 059, 621)
inferential statistics
numerical data that allow one to generalize—to infer from sample data the probability of something being true of a population. (Myers Psychology for AP 2e p. 060)
statistical significance
a statistical statement of how likely it is that an obtained result occurred by chance. (Myers Psychology for AP 2e p. 060)
culture
the enduring behaviors, ideas, attitudes, values, and traditions shared by a group of people and transmitted from one generation to the next. (Myers Psychology for AP 2e pp. 065, 776)
informed consent
an ethical principle that research participants be told enough to enable them to choose whether they wish to participate. (Myers Psychology for AP 2e p. 068)
debriefing
the post-experimental explanation of a study, including its purpose and any deceptions, to its participants. (Myers Psychology for AP 2e p. 068)
placebo effect
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. (Myers Psychology for AP 2e p. 052)