AP Psych Terms 2025/2026 EDITION
experiment == a scientific procedure undertaken to make a discovery, test a hypothesis, or
demonstrate a known fact.
independent variable == variable that is manipulated
dependent variable == The measurable effect, outcome, or response in which the research is
interested.
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.
Placebo == A harmless pill, medicine, or procedure prescribed more for the psychological
benefit to the patient than for any physiological effect.
single-blind study == study in which the subjects do not know if they are in the experimental or
the control group
double-blind study == An experiment in which neither the participant nor the researcher knows
whether the participant has received the treatment or the placebo
random assignment == assigning participants to experimental and control conditions by chance,
thus minimizing preexisting differences between those assigned to the different groups
random selection == procedure that ensures every person in a population has an equal chance of
being chosen to participate
Sampling == The process of selecting representative units from a total population
case study == an observation technique in which one person is studied in depth in the hope of
revealing universal principles
correlational research == research that seeks to identify whether an association or relationship
between two factors exists
Meta-analysis research == Seek patterns in data collected by many existing studies and formulate
principals
naturalistic observation == observing and recording behavior in naturally occurring situations
without trying to manipulate and control the situation
,Hypothesis == A testable prediction, often implied by a theory
Operational definition of a variable == description of how variables will be measured or
manipulated in a study
sampling bias == A problem that occurs when a sample is not representative of the population
from which it is drawn.
experimental bias == a mistake in the design of an experiment that makes a particular result
more likely
generalization == A conclusion drawn from specific information that is used to make a broad
statement about a topic or person
peer review == A process by which the procedures and results of an experiment are evaluated by
other scientists who are in the same field or who are conducting similar research.
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
Mode == the most frequently occurring score(s) in a distribution
range == the difference between the highest and lowest scores in a distribution
normal distribution curve == 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.
standard deviation == a measure of variability that describes an average distance of every score
from the mean
Correlation Coefficient == A numerical index of the degree of relationship between two
variables.
longitudinal study == a study that observes the same participants on many occasions over a long
period of time
cross-sectional study == a study in which people of different ages are compared with one another
Hawthorne effect == the tendency for people to behave differently when they know they are
being studied
confounding variable == a factor other than the independent variable that might produce an
effect in an experiment
, quasi-experiment == An experiment in which investigators make use of control and experimental
groups that already exist in the world at large. Also called a mixed design. No random
assignment.
Lab experiment == An experiment that takes place in a controlled environment where the
researcher manipulates the IV and records the effect on the DV while maintaining strict control
of extraneous variables.
field experiment == An experiment that takes place in a natural setting where the researcher
manipulates the IV and records the effect on the DV.
natural experiment == An experiment in which nature, rather than an experimenter, manipulates
an independent variable.
Heredity == the transmission of traits from one generation to the next
behavior genetics == How much our genes and our environment influence our individual
differences
environment == the surroundings or conditions in which a person, animal, or plant lives or
operates.
interactionist approach == The idea that nature and nurture are linked to such an extent that it
does not make sense to separate the two, so researchers instead study how they interact and
influence each other.
Chromosomes == threadlike structures made of DNA molecules that contain the genes
DNA == deoxyribonucleic acid, a complex molecule containing the genetic information that
makes up the chromosomes.
Genes == DNA segments that serve as the key functional units in hereditary transmission.
Genome == All the genetic information in an organism; all of an organism's chromosomes.
Monozygotic == developed from a single fertilized ovum, as identical twins
Dizygotic == twins from two separate zygotes, fraternal
Heritability == The proportion of variation among individuals that we can attribute to genes. The
heritability of a trait may vary, depending on the range of populations and environments studied.
Epigenetics == the study of environmental influences on gene expression that occur without a
DNA change
experiment == a scientific procedure undertaken to make a discovery, test a hypothesis, or
demonstrate a known fact.
independent variable == variable that is manipulated
dependent variable == The measurable effect, outcome, or response in which the research is
interested.
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.
Placebo == A harmless pill, medicine, or procedure prescribed more for the psychological
benefit to the patient than for any physiological effect.
single-blind study == study in which the subjects do not know if they are in the experimental or
the control group
double-blind study == An experiment in which neither the participant nor the researcher knows
whether the participant has received the treatment or the placebo
random assignment == assigning participants to experimental and control conditions by chance,
thus minimizing preexisting differences between those assigned to the different groups
random selection == procedure that ensures every person in a population has an equal chance of
being chosen to participate
Sampling == The process of selecting representative units from a total population
case study == an observation technique in which one person is studied in depth in the hope of
revealing universal principles
correlational research == research that seeks to identify whether an association or relationship
between two factors exists
Meta-analysis research == Seek patterns in data collected by many existing studies and formulate
principals
naturalistic observation == observing and recording behavior in naturally occurring situations
without trying to manipulate and control the situation
,Hypothesis == A testable prediction, often implied by a theory
Operational definition of a variable == description of how variables will be measured or
manipulated in a study
sampling bias == A problem that occurs when a sample is not representative of the population
from which it is drawn.
experimental bias == a mistake in the design of an experiment that makes a particular result
more likely
generalization == A conclusion drawn from specific information that is used to make a broad
statement about a topic or person
peer review == A process by which the procedures and results of an experiment are evaluated by
other scientists who are in the same field or who are conducting similar research.
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
Mode == the most frequently occurring score(s) in a distribution
range == the difference between the highest and lowest scores in a distribution
normal distribution curve == 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.
standard deviation == a measure of variability that describes an average distance of every score
from the mean
Correlation Coefficient == A numerical index of the degree of relationship between two
variables.
longitudinal study == a study that observes the same participants on many occasions over a long
period of time
cross-sectional study == a study in which people of different ages are compared with one another
Hawthorne effect == the tendency for people to behave differently when they know they are
being studied
confounding variable == a factor other than the independent variable that might produce an
effect in an experiment
, quasi-experiment == An experiment in which investigators make use of control and experimental
groups that already exist in the world at large. Also called a mixed design. No random
assignment.
Lab experiment == An experiment that takes place in a controlled environment where the
researcher manipulates the IV and records the effect on the DV while maintaining strict control
of extraneous variables.
field experiment == An experiment that takes place in a natural setting where the researcher
manipulates the IV and records the effect on the DV.
natural experiment == An experiment in which nature, rather than an experimenter, manipulates
an independent variable.
Heredity == the transmission of traits from one generation to the next
behavior genetics == How much our genes and our environment influence our individual
differences
environment == the surroundings or conditions in which a person, animal, or plant lives or
operates.
interactionist approach == The idea that nature and nurture are linked to such an extent that it
does not make sense to separate the two, so researchers instead study how they interact and
influence each other.
Chromosomes == threadlike structures made of DNA molecules that contain the genes
DNA == deoxyribonucleic acid, a complex molecule containing the genetic information that
makes up the chromosomes.
Genes == DNA segments that serve as the key functional units in hereditary transmission.
Genome == All the genetic information in an organism; all of an organism's chromosomes.
Monozygotic == developed from a single fertilized ovum, as identical twins
Dizygotic == twins from two separate zygotes, fraternal
Heritability == The proportion of variation among individuals that we can attribute to genes. The
heritability of a trait may vary, depending on the range of populations and environments studied.
Epigenetics == the study of environmental influences on gene expression that occur without a
DNA change
