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chisquare distribution
A family of distributions associated with the chisquare statistic

Constant
A construct that has only one value (e.g., if every member of a sample was 10 years old, the "age" construct would be a constant).

Convenience sampling
Selecting a sample based on ease of access or availability

Correlational research design
A style of research used to examine the associations among variables. Variables are not manipulated by the researcher in this type of research design.

Dependent variable
The values of the dependent variable are hypothesized to depend on the values of the independent variable. For example, high depends, in part, on gender.

Descriptive statistics
Statistics used to describe the characteristics of a distribution of scores

Dichotomous variable
A variable that has only two discrete values (e.g., a pregnancy variable can have a value of 0 for "not pregnant" and 1 for "pregnant").

Distribution
Any collection of scores on a variable

Experimental research design
A type of research in which the experimenter, or researcher, manipulates certain aspects of the research. These usually include manipulations of the independent variable and assignment of cases to groups.

F Distributions
A family of distributions associated with the F statistic, which is commonly used in analysis of variance (ANOVA).

Frequency
How often a score occurs in a distribution.

Generalize (or generalizability)
The ability to use the results of data collected from a sample to reach conclusions about the characteristics of the population, or any other case not included in the sample.

Independent variable
A variable on which the values of the dependent variable are hypothesized to depend. Independent variables are often, but not always, manipulated by the researcher.

Inferential statistics
Statistics, derived from sample data, that are used to make inferences about the population from which the sample was drawn.

Interval or Ratio variable
Variables measured with numerical values with equal distance, or space, between each number (e.g., 2 is twice as much as 1, 4 is twice as much as 2, the distance between 1 and 2 is the same as 2 and 3).

Mean
the arithmetic average of a distribution of scores

Nominally scales variable
A variable in which the numerical values assigned to each category are simply labels rather than meaningful numbers.

Normal distribution
A variable in which the numerical values assigned to each category are simply labels rather than meaningful numbers.

Ordinal variable
Variables measured with numerical values where the numbers are meaningful (e.g., 2 is larger than 1) but the distance between the numbers is not constant.

Parameter
A value, or values, derived from population data

Population
The collection of cases that comprise the entire set of cases with the specified characteristics (e.g., all living adult males in the United States).

Qualitative (or categorical) variable
A variable that has discrete categories. If categories are given numerical values, the values have meaning as nominal references but not as numerical values (e.g., in 1=male and 2=female, 1 is not more or less than 2)

Quantitative (or continuous) variable
A variable that has assigned values and the values are ordered and meaningful, such that 1 is less than 2, 2 is less than 3, and so on.

Random Assignment
assignment members of a sample to different groups (e.g., experimental and control) randomly, or without consideration of any of the characteristics of sample members.

Random Sample (or random sampling)
Selecting cases from a population in a manner that ensures each member of the population has an equal chance of being selected into the sample.

Representative Sampling
A method of selecting a sample in which members are purposely selected to create a sample that represents the population on some characteristic(s) of interest (e.g., when a sample is selected to have the same percentages of various ethnic groups as the larger population).

Sample
A collection of cases selected from a larger population

Statistic
a characteristic, or value, derived from sample data

t distributions
A family of distributions associated with the t statistic, commonly used in the comparison of sample means and tests of statistical significance for correlation coefficients and regression slopes

Variable
Any construct with more than one value that is examined in research.

