Variables that are associated with one another numerically. Also called dependent variables.

An individual in a sample dataset on whom one or more variables have been measured. Also called an observational unit.

A variable with values (levels) that represent categories.

A relationship between variables in which changing the value of one variable has an affect on the value of another variable.

A group of individuals (cases) who share some characteristic(s) (e.g., all born in the same year).

A numerical variable that can take any numerical value within an interval (e.g., a decimal number between 0 and 1).

Cases in the sample who do not receive a specific treatment being investigated.

Measurements of one or more variables on a sample of observations.

A common way to organize data in which the matrix rows represent cases (observational units) and the matrix columns represent variables.

Variables that are associated with one another numerically. Also called associated variables. [The term "dependent variable" is sometimes used for a "response variable," but that convention is not used in this course.]

A numerical variable that can only take numerical values with gaps between them (e.g., 0, 1, 2, ...).

A study in which researchers conduct an experiment to investigate the possibility of a causal connection between variables by controlling the values of the explanatory variable(s) for selected cases.

When we suspect one variable might causally affect another, we label the first variable the
explanatory variable. Also called a predictor variable.

Two variables that are not associated and have no evident relationship. [Do not mix this up with the concept of independent events in probability. Also the term "independent variable" is sometimes used for an "explanatory variable," but that convention is not used in this course.]

The possible values of a categorical variable.

An association between two numerical variable in which an increase in one variable tends to be associated with a decrease in the other variable.

A categorical variable in which the levels have no meaningful, natural order.

A variable that can take a range of numerical values, and it is meaningful to add, subtract, or take averages with those values. Also called a quantitative variable.

A study in which researchers collect data in a way that does not directly interfere with how the data arise.

An individual in a sample dataset on whom one or more variables have been measured. Also called a case.

A categorical variable in which the levels have a meaningful, natural order.

A "sham" treatment with no known impact on a response variable (e.g., a sugar pill).

An association between two numerical variables in which an increase in one variable tends to be associated with an increase in the other variable.

When we suspect one variable might causally affect another, we label the first variable the
explanatory variable. Also called an explanatory variable.

A variable that can take a range of numerical values, and it is meaningful to add, subtract, or take averages with those values. Also called a numerical variable.

An experiment in which individuals (cases) are randomly assigned to a group (e.g., "treatment" or "control").

When we suspect one variable might causally affect another, we label the second variable the
response variable.

A graph of two numerical variables in which each sample point is plotted at the intersection of the value of one variable on the horizontal axis and the other variable on the vertical axis.

The study of how best to collect, analyze, and draw conclusions from data.

A single number summarizing the values of a variable for a sample of observations.

Cases in the sample who receive a specific treatment being investigated.

A characteristic of an observational unit that has been measured.