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Information collected in narrative form.
Qualitative data
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Information collected in numeric form.
Quantitative data
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Variable hypothesized cause of or influence on the dependent variable.
Independent Variable
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Variable hypothesized to depend on or be caused by another variable; the outcome of interest.
Dependent Variable
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Having a finite number of values between any two points.
Discrete
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Able to take on an infinite (in theory) range of values between two points on a continuum.
Continuous
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The assignment of numbers to objects to designate the quantity of an attribute, according to specified rules.
Measurement
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Lowest level of measurement; involving the assignment of characteristics into categories with no particular order.
Nominal
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Level of measurement that yields a rank ordering of a variable along a specified dimension.
Ordinal
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Level of measurement that involves assigning numbers to indicate both the ordering on an attribute and the distance between different amounts of the attribute.
Interval
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Level of measurement of attributes in which there are equal distances between score units and a true meaningful zero point.
Ratio
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Collective term for interval or ratio data.
Scale
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Statistics used to describe and summarize data.
Descriptive Statistics
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Statisticsthat rely on the laws of probability to help researchers draw conclusions about sample characteristics in terms of their relationship to populations.
Inferential Statistics
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The entire set of individuals having some characteristic.
Population
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A subset of a population selected for study.
Sample
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Systematic array of data values together with a count of the number of times each value was obtained.
Frequency distribution
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The count of the number of cases with a given score value.
Absolute frequency
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A grouping of continuous variable data such that is can be displayed in a grouped frequency distribution.
Class intervals
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A graphical display of a frequency distribution, generally for a
categorical variable.
Bar graph/chart
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A graphical display showing a relative frequency distribution in a circle.
Pie Chart
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A graphical display of a frequency distribution in which dots connected by a straight line indicate the number of times a score value occurs.
Frequency polygon
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Characteristic
of a frequency distribution describing the number of peaks.
Modality
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Having one peak.
Unimodal
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A distribution with two sides that are mirror images; a non-skewed
distribution.
Symmetric distribution
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A distribution that is asymmetric.
Skewed distribution
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A distribution with a pointed, thin peak.
Leptokurtic
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A distribution with a low, wide-spread peak.
Playkurtic
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Theoretical distribution that is symmetrical, unimodal, not too peaked, nor too flat.
Normal distribution
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Indexes that come from the center of a distribution, describing a “typical” value.
Measures of Central Tendency
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The score or value that occurs most frequently in a distribution.
Mode
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The exact middle score in a distribution; the score above and below which 50% of the scores lie.
Median
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The arithmetic average of a distribution, calculated by summing all scores and dividing by the number of scores.
Median
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The difference between the highest and lowest value in a distribution.
Range
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A descriptive statistic for measuring the degree of variability in a set
of score
Standard deviation
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A measure of dispersion of a distribution; equal to the standard deviation squared.
Variance
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Scores or values expressed in terms of standard deviations away from the mean.
Standard scores
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Standard scores when the distribution is normal.
Z scores
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Two-dimensional table that displays a crosstabulation of two categorical variables.
Contingency table
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Two-dimensional table that displays a crosstabulation of two categorical variables.
Contingency table
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A relationship between two continuous variables such that, when plotted in a scatterplot, a straight line is formed.
Linear relationship
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A graph depicting the relationship between two continuous variables.
Scatterplot
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An index that summarizes the magnitude and direction of the relationship between two variables.
Correlation coefficient
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A relationship in which high values of one variable are associated with high values in another variable.
Positive relationship
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A relationship in which high values of one variable are associated with low values in another variable.
Negative relationship
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Designates the magnitude and direction of the relationship between two measured on at least the interval level.
Pearson’s r
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