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Population
An entire set of objects, individuals, or objects that are being studied.
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Sample
A subset or a portion of a population.
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Variable
- A characteristic or attribute about each subject of a population or sample that can assume different values.
- (For example, if we measured the reaction time of 10 subjects, then reaction time will be a variable.)
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Data
The values—measurements or observations—that the variables can assume. With a singular data point we are referring to the value of the variable associated with one subject from our sample.
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Data set
A collection of data values for a variable from each of the subjects or participants in a sample.
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Parameter
A measurement that describes a characteristic of a population. A parameter is a value that describes the entire population.
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Statistic
A statistic describes a characteristic of a sample. It is a numerical value that summarizes the sample data.
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Descriptive Statistics
Procedures for organizing and summarizing data so that the important characteristics can be described and communicated.
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Inferential Statistics
Procedures for determining whether sample data represent a particular relationship in the population.
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Design
The way in which a study is laid out.
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Independent Variable
In an experiment, a variable that is changed or manipulated by the experimenter; a variable hypothesized to cause a change in the dependent variable.
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Random Sampling
A method of selecting samples so that all members of the population have the same chance of being selected for a sample.
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Measure of Central Tendency
Statistics that summarize the location of a distribution on a variable by indicating where the center of the distribution tends to be located.
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Mean
The score located at the mathematical center of a distribution.
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Statistical Hypotheses
Two statements that describe the population parameters the sample statistics will represent if the predicted relationship exists or does not exist.
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Alternative Hypothesis (Ha)
The hypothesis describing the population parameters that the sample data represent if the predicted relationship does exist.
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Null Hypothesis (H0)
The hypothesis describing the population parameters that the sample data represent if the predicted relationship does not exist.
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criterion
The probability that defines whether a sample is unlikely to have occurred by chance and thus is unrepresentative of a particular population.
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region of rejection
That portion of a sampling distribution containing values considered too unlikely to occur by chance, found in the tail or tails of the distribution.
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critical value
The score that marks the inner edge of the region of rejection in a sampling distribution; values that fall beyond it lie in the region of rejection.
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z-distribution
The distribution of z-scores produced by transforming all raw scores in a distribution into z-scores.
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