hindsight bias
the tendency to believe, after learning an outcome, that one would have foreseen it
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 carefully worded statement of the exact procedures used in a research study
Replication
repeating the essence of a research study, usually with different participants in different situations, to see whether the basic finding can be reproduced
case study
a descriptive technique in which one individual or group is studied in depth in the hope of revealing universal principles
naturalistic observation
a descriptive technique of observing and recording behavior in naturally occurring situations without trying to manipulate and control the situation
survey
a descriptive technique for obtaining the self-reported attitudes or behaviors of a particular group, usually by questioning a representative, random sample of the group
sampling bias
a flawed sampling process that produces an unrepresentative sample
Population
all those in a group being studied, from which samples may be drawn
random sample
a sample that fairly represents a population because each member has an equal chance of inclusion
Correlation
A measure of the extent to which two factors vary together, and thus of how well either factor predicts the other
correlation coefficient
a statistical index of the relationship between two things (from -1 to +1)
Variable
anything that can vary and is feasible and ethical to measure
Scatterplot
a graphed cluster of dots, each of which represents the values of two variables
illusory correlation
perceiving a relationship where none exists, or perceiving a stronger-than-actual relationship
regression toward the mean
the tendency for extreme or unusual scores to fall back (regress) toward their average.
experiment
A research method in which an investigator manipulates one or more factors to observe the effect on some behavior or mental process
experimental group
In an experiment, the group that is exposed to the treatment, that is, to one version of the independent variable.
control group
In an experiment, the group that is not exposed to the treatment; contrasts with the experimental group 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
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
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.
independent variable
in an experiment, the factor that is manipulated; the variable whose effect is being studied
confounding variable
a factor other than the factor being studied that might influence a study's results
dependent variable
in an experiment, the outcome that is measured; the variable that may change when the independent variable is manipulated
Validity
the extent to which a test measures or predicts what it is supposed to
informed consent
giving potential participants enough information about a study to enable them to choose whether they wish to participate
Debriefing
the post-experimental explanation of a study, including its purpose and any deceptions, to its participants
descriptive statistics
numerical data used to measure and describe characteristics of groups. Includes measures of central tendency and measures of variation.
Histogram
a bar graph depicting a frequency distribution
Mode
the most frequently occurring score(s) 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
skewed distribution
a representation of scores that lack symmetry around their average value
range
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
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.
inferential statistics
numerical data that allow one to generalize- to infer from sample data the probability of something being true of a population
statistical significance
a statistical statement of how likely it is that an obtained result occurred by chance