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Chapter 2 key terms from AP Psychology Zimbardo textbook.

Scientific Method

A five-step process for empirical investigation of a hypothesis under conditions designed to control biases and subjective judgments.

Empirical Investigation

An approach to research that relies on sensory experience and observation as research data.

Theory

A testable explanation for a set of facts or observations.

Hypothesis

A statement predicting the outcome of a scientific study; a statement describing the relationship among variables in a study.

Operational Definition

Specific descriptions of concepts involving the conditions of a scientific study.

Independent Variable

A stimulus condition so named because the experimenter changes it independently of all the other carefully controlled experimental conditions.

Random Presentation

A process by which chance alone determines the order in which the stimulus is presented.

Data

Pieces of information, especially information gathered by a researcher to be used in testing a hypothesis.

Dependent Variable

The measured outcome of a study; the responses of the subjects in a study.

Replicate

In research this refers to doing a study over to see whether the same results are obtained. As a control for bias, replication is often done by someone other than the researcher who performed the original study.

Experiment

A kind of research in which the researcher controls all the conditions and directly manipulates the conditions, including the independent variable.

Confounding/Extraneous Variables

Variables that have an unwanted influence on the outcome of an experiment.

Controls

Constraints that the experimenter places on the experiment to ensure that each subject has the exact same conditions.

Random Assignment

Each subject of the sample has an equal likelihood of being chosen for the experimental group of an experiment.

Ex Post Facto

Research in which we choose subjects based on a pre-existing condition.

Correlational Study

A type of research that is mainly statistical in nature.

Survey

A quasi-experimental method in which questions are asked to subjects.

Naturalistic Observation

A research method in which subjects are observed in their natural environment.

Longitudinal Study

A type of study in which one group of subjects is followed and observed.

Cross-Sectional Study

A study in which a representative cross section of the population is tested or surveyed at one specific time.

Cohort-Sequential Study

A research method in which a cross section of the population is chosen and then each cohort is followed for a short period of time.

Personal Bias

The researcher allowing personal beliefs to affect the outcome of a study.

Expectancy Bias

The researcher allowing his or her expectations to affect the outcome of a study.

Double-Blind Study

An experimental procedure in which both researchers and participants are uninformed about the nature of the independent variable being administered.

Institutional Review Board

A committee at each institution where research is conducted to review every experiment for ethics and methodology.

Institutional Animal Care and Use Committee

A committee at each institution where research is conducted to review every experiment involving animals for ethics and methodology.

ABCs of Laboratory Animal Research

Guiding principles in which research on animals is conducted. Governs the morality and ethical aspect of research on animals.

Frequency Distribution

A summary chart, showing how frequently each of the scores in a set of data occurs.

Histogram

A bar graph depicting a frequency distribution. The height of the bars indicates the frequency of a group of scores.

Descriptive Statistics

Statistical procedures used to describe characteristics and responses of groups of subjects.

Mean

The measure of central tendency most often used to describe a set of data--calculated by adding all the scores and diving by the number of scores. (mathematical average)

Median

The measure of central tendency for a distribution, represented by the score the separates the upper half of the scores in a distribution from the lower half.

Mode

A measure of central tendency for a distribution, represented by the score that separates the upper half scores in a distribution from the lower half.

Range

The simplest measure of variability, represented by the difference between the highest and the lowest values in a frequency distribution.

Standard Deviation

A measure of variability that indicates the average difference between the scores and their mean.

Correlation

A relationship between variables, in which changes in one variable are reflected in changes in the other variable.

Normal Distribution

A bell-shaped curve, describing the spread of a characteristic throughout a population.

Correlation Coefficient

A number between -1 and +1 expressing the degree of relationship between two variables.

Inferential Statistics

Statistical techniques used to assess whether the results of a study are reliable or whether they might be simply the result of a chance.

Random Sample

A sample group of subjects selected by chance.

Representative Sample

A sample obtained in such a way that it reflects the distribution of important variables in the larger population in which the researchers are interested.

Significant Difference

Psychologists accept a difference between the groups as "real", or significant, when the probability that it might be due to an atypical sample drawn by chance is less than 5 in 100.

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