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.

### 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.

### 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.

### Naturalistic Observation

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

### 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.

### 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.

### 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.