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### Scientific Method

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

### Empirical Investigation

Approach to research that relies on sensory experience and observation as research data

### Theory

Testable explanation for a set of facts or observations. In science, a theory is not just speculation or a guess

### Hypothesis

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

### Operational Definition

Specific descriptions of concepts involving the conditions of a scientific study; stated in terms of how the concepts are to be measured or what operations are being employed

### Independent Variable

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

### Experiment

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 experiment group of an experiment

### Correlational Study

Type of research that is mainly statistical in nature. Determines the relationship between two variables

### Survey

Quasi-experimental method in which questions are asked to subjects. Questions must not be skewed or biased

### Naturalistic Observation

Research method in which subjects are observed in their natural environment

### Longitudinal Study

Type of study in which one group of subjects is followed an observed for an extended period of time

### Cross-Sectional Study

Study in which a representative cross-section of the population is tested or surveyed at one specific time

### Cohort-Sequential Study

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

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

### Institutional Review Board(IRB)

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

### ABC'S of Laboratory Animal Research

All animal research must comply with ABC's of laboratory animal research; appropriate, beneficial, and caring

### Frequency Distribution

Summary chart showing how frequently each of the various scores in a set of data occurs

### Histogram

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

Measure of central tendency most often used to describe a set of data-- calculated by adding all the scores and dividing by the number of scores

### Median

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

### Mode

Measure of central tendency for a distribution, represented by the score that occurs more often than any other

### Range

Simplest measure of variability represented by the difference between the highest and the lowest values in a frequency distribution

### Standard Deviation

Measure of variability that indicates the average difference between the scores and their mean

### Correlation

Relationship between variables in which changes in one variable-- as in the correlation between a child's age and height

### Normal Distribution

Bell-shaped curve, describing the spread of a characteristic throughout a population

### Correlation Coefficient

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 chance. Often used to determine whether two or more groups are essentially the same or different

### Representative Sample

Sample obtained in a such a way that it reflects the distribution of important variables in the larger population in which the researchers are interested- variables such as age, income level, ethnicity, and geographic distribution