Princeton AP Psych 22nd: Foundations: Methods & Approaches

experiment

an investigation seeking to understand relations of cause and effect

independent variable

the manipulated variable

dependent variable

the measured variable

control variable

the constant in both groups

population

group of interest

representative sample

a subset of a population that accurately mirrors the characteristics, demographics, and behaviors of the broader group

representativeness

the degree to which a sample reflects the diverse characteristics of the population that is being studied

random sampling

a way of ensuring maximum representativeness

random assigned

done to ensure that each group has minimal differences

experimental group

the group receiving or reacting to the independent variable

control group

does not receive the independent variable but should be kept identical in all other respects

biases

Favoring of or against one person, group or thing compared with another, usually in a way considered to be unfair

bias of selection

when people are selected in a physical space

self-selection bias

when the people being studied have some control over whether or not to participate

pre-screening/advertising bias

often in medical research; how volunteers are screened or where advertising is placed might skew the sample

healthy user bias

when the study population tends to be in better shape than the general population

single-blind design

the subjects do not know whether they are in the control or experimental group

double-blind design

neither the subjects nor the researcher knows who is in the two groups

placebo

a seemingly therapeutic object or procedure, which causes the control group to believe they could be in the experimental group but actually contains none of the tested material

correlational research

assessing the degree of association between two or more variables or characteristics of interest that occur naturally

confounding variable/third variable/extraneous variable

an unknown factor is playing a role

surveys

questionnaires or interviews for correlational studies

clinical research

research in which people, or data or samples of tissue from people, are studied to understand health and disease

case studies

intensive psychological studies of single individuals

generalizable

applicable to similar circumstances because of the predictable outcomes of repeated tests

longitudinal studies

happen over long periods of time with the same subjects

cross-sectional studies

designed to test a wide array of subjects from different backgrounds to increase generalizability

conceptual definition

the theory or issue being studied

operational definition

the way in which that theory or issue will be directly observed or measured in the study

internal validity

the certainty with which the results of an experiment can be attributed to the manipulation of the independent variable rather than to some other, confounding variable (related to operational defintions)

external validity

the extent to which the findings of a study can be generalized to other contexts in the real world (related to the operational definitions)

reliability

the same results appear if the experiment is repeated under similar conditions

inter-rater reliability

the degree to which different raters agree on their observations of the same data

naturalistic observation

watching and studying phenomena as they naturally occur in the environment

qualitative research

provides detailed descriptions of experience rather than the numerical data of quantitative methods (e.g. case studies, phenomenological studies, ethnographic studies, narrative studies, and grounded theory)

descriptive statistics

summarize data

inferential statistics

allow researchers to test hypotheses about data and determine how confident they can be in their inferences about the data

central tendency

characterize the typical value in a set of data

mean

the arithmetic average of a set of numbers

mode

the most frequently occurring value in the data set

bimodal distribution

when two numbers both appear with the greatest frequency

median

the number that falls exactly in the middle of a distribution of numbers

normal curve

when the mean, median, and mode are identical

range

the largest number minus the smallest number

variability

how much the numbers in the set differ from one another

standard deviation

measures a function of the average dispersion of numbers around the mean and is a commonly used measure of variability

percentile

the standing of one score relative to all other scores in a set of data

positive skew/skewed right

most values are on the lower end, but there are some exceptionally large values

negative skew/skewed left

most values are on the higher end, but there are some exceptionally small values

correlation coefficient

a numerical value that indicates the degree and direction of the relationship between two variables

Pearson correlation coefficient

a specific type of correlation that describes how close to linear the relationship between two attributes is

sample size

the number of observations or individuals measured

null hypothesis

a treatment had no effect in an experiment

alternative hypothesis

the treatment did have an effect

alpha

the accepted probability that the result of an experiment can be attributed to chance rather than the manipulation of the independent variable

Type I error/false positive

the conclusion that a difference exists when, in fact, this difference does not exist

Type II error/false negative

the conclusion that there is no difference when, in fact, there is a difference

p-value

• the results are statistically significant (not due only to chance)

• the probability of making a Type I error

deception

the act of deliberately causing somebody to accept something as true that is not true

Stanley Milgram

conducted obedience experiments in which he convinced participants that they were administering painful electric shocks to other participants, when, in fact, no shocks were given

confederates

people were are aware of the true nature of the experiment but pretended to be participants

Institutional Review Boards (IRBs)

assess research plans before the research is approved to ensure that it meets all ethical standards

informed consent

participants agree to participate in the study only after they have been told what their participation entails

debriefing

participants are told the exact purpose of their participation in the research and of any deception that may have been used in the process of experimentation