Two Variable Statistics

Front 1

Correlation

Back 1

A relationship that exists when one event can be used to predict a second event; if A correlates to B, B correlates to A.

Front 2

Positive Correlation

Direct Relationship

Back 2

As A increases, so does B.

As X increases, so does Y.

Front 3

Negative Correlation

Indirect Relationship

Back 3

As A increases, B decreases and vice versa.

As X increases, Y decreases and vice versa.

Front 4

Zero Correlation

Back 4

There is no correlation between the data sets—no relationship exists between the x and y variables.

Front 5

Correlation Coefficient (r)

Back 5

Indicates both the strength and thedirection of the relationship between the variables of a scatter plot; will always be a number between -1 and +1.

-r (-1 to 0) = indirect; +r (0 to 1) = direct;

if r is equal to, or close to, zero = no correlation

Front 6

Covariance

Back 6

A measure of how two quantities change together.

Front 7

Causation

Back 7

Occurs when one of two correlated events functions asa cause of the other; if A causes B, B cannot cause A.

Correlation does not imply causation, but causation impliescorrelation.

Front 8

Experiment

Back 8

A study in which researchers directly influence thesubjects. Experiments can determine causation.

Front 9

Control Group

Back 9

In an experiment, the test subjects that do notreceive the treatment under investigation.

Front 10

Treatment Group

Back 10

The test subjects in an experiment who doreceive the treatment under investigation.

Front 11

Blind Experiment

Back 11

Fake treatments are given to the controlgroup and experimental treatments to the treatment group. Alltest subjects are unaware of which treatment they receive.

Front 12

Double-Blind Experiment

Back 12

When neither the subjects nor the researchers know what groupa subject belongs to.

Front 13

Confounding Variables

Back 13

Outside factors that may alter anoutcome.

Front 14

Independent Variable

Back 14

The variable that is manipulated in theexperiment. In a perfect experiment, the independent variable isthe only difference between the treatment group and the controlgroup.

Front 15

Dependent Variable

Back 15

The variable being measured in anexperiment—specifically, how it is affected or not affected by achange in the independent variable.

Front 16

Placebo Effect

Back 16

A confounding variable that occurs whenthe thought of being tested or treated causes a reaction from thesubject.

Front 17

Observational Study

Back 17

A study in which researchers collect datathrough observation. These studies only demonstrate correlationand can never be used to prove causation.

Front 18

Retrospective Study

Back 18

A study in which a researcher looks backwardat an outcome.

Front 19

Prospective Study

Back 19

A study in which a researcher looks forward toan outcome that has yet to occur.

Front 20

Blocking

Back 20

Dividing subjects into blocks according to a confoundingvariable and randomly assigning members of each block into thetreatment and control groups.

Front 21

Scatter Plot

Back 21

A graph that describes the relationship between twosets of quantitative data.

Front 22

Linear Relationship

Back 22

When the points on a scatter plot forma line.