
Information collected in narrative form.
Qualitative data

Information collected in numeric form.
Quantitative data

Variable hypothesized cause of or influence on the dependent variable.
Independent Variable

Variable hypothesized to depend on or be caused by another variable; the outcome of interest.
Dependent Variable

Having a finite number of values between any two points.
Discrete

Able to take on an infinite (in theory) range of values between two points on a continuum.
Continuous

The assignment of numbers to objects to designate the quantity of an attribute, according to specified rules.
Measurement

Lowest level of measurement; involving the assignment of characteristics into categories with no particular order.
Nominal

Level of measurement that yields a rank ordering of a variable along a specified dimension.
Ordinal

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

Level of measurement of attributes in which there are equal distances between score units and a true meaningful zero point.
Ratio

Collective term for interval or ratio data.
Scale

Statistics used to describe and summarize data.
Descriptive Statistics

Statisticsthat rely on the laws of probability to help researchers draw conclusions about sample characteristics in terms of their relationship to populations.
Inferential Statistics

The entire set of individuals having some characteristic.
Population

A subset of a population selected for study.
Sample

Systematic array of data values together with a count of the number of times each value was obtained.
Frequency distribution

The count of the number of cases with a given score value.
Absolute frequency

A grouping of continuous variable data such that is can be displayed in a grouped frequency distribution.
Class intervals

A graphical display of a frequency distribution, generally for a
categorical variable.
Bar graph/chart

A graphical display showing a relative frequency distribution in a circle.
Pie Chart

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

Characteristic
of a frequency distribution describing the number of peaks.
Modality

Having one peak.
Unimodal

A distribution with two sides that are mirror images; a nonskewed
distribution.
Symmetric distribution

A distribution that is asymmetric.
Skewed distribution

A distribution with a pointed, thin peak.
Leptokurtic

A distribution with a low, widespread peak.
Playkurtic

Theoretical distribution that is symmetrical, unimodal, not too peaked, nor too flat.
Normal distribution

Indexes that come from the center of a distribution, describing a “typical” value.
Measures of Central Tendency

The score or value that occurs most frequently in a distribution.
Mode

The exact middle score in a distribution; the score above and below which 50% of the scores lie.
Median

The arithmetic average of a distribution, calculated by summing all scores and dividing by the number of scores.
Median

The difference between the highest and lowest value in a distribution.
Range

A descriptive statistic for measuring the degree of variability in a set
of score
Standard deviation

A measure of dispersion of a distribution; equal to the standard deviation squared.
Variance

Scores or values expressed in terms of standard deviations away from the mean.
Standard scores

Standard scores when the distribution is normal.
Z scores

Twodimensional table that displays a crosstabulation of two categorical variables.
Contingency table

Twodimensional table that displays a crosstabulation of two categorical variables.
Contingency table

A relationship between two continuous variables such that, when plotted in a scatterplot, a straight line is formed.
Linear relationship

A graph depicting the relationship between two continuous variables.
Scatterplot

An index that summarizes the magnitude and direction of the relationship between two variables.
Correlation coefficient

A relationship in which high values of one variable are associated with high values in another variable.
Positive relationship

A relationship in which high values of one variable are associated with low values in another variable.
Negative relationship

Designates the magnitude and direction of the relationship between two measured on at least the interval level.
Pearson’s r

