AP Statistics Chapter 7
When describing a scatterplot, what four things should you always mention?
1. Direction 2. Form 3. How strong the relationship is 4. The unexpected
What three conditions are necessary in order to use correlation as a measure of association?
1. Quantitative Variables 2. Straight Enough 3. Outliers
Association
A comparison or connection of a scatterplot
Scatter
Amount of space in scatterplot
Explain the difference between association and correlation?
Association-Relationship Correlation-Measuring
What does a correlation near 1 or -1 indicate?
Data falls exactly in a straight line
Response variable
Dependent variable on the y-axis, responds to explanatory variable
What does the sign of the correlation coefficient tell you about the association?
Describes the direction and magnitude of the relationship
Scatterplot
Display for quantitative variables that shows patterns, trends, relationships and outliers of the variables.
Correlation Coefficient
Measures the strength of the linear association between two quantitative variables.
Direction
Negative-Runs from upper left to lower right Positive-Runs from lower left to upper right
Is correlation resistant or nonresistant to outliers?
Nonresistant because the correlation adjusts to include the outlier, so the result could be changed dramatically with the outlier.
Form
Particular type of data they contain
What type of graph is used to show the relationship between two quantitative variables?
Scatterplot
What is it meant by an explanatory variable?
The independent variable on the x axis (X variable)
What does correlation measure?
The strength of the linear relationship between two quantitative variables.
What is it meant by a response variable?
The variable of interest, respondent to the explanatory variable. Graphed on the y axis
What does a correlation near 0 indicate?
Weakest linear relationship
Explanatory variable
X-variable on the x-axis, independent variable
Sketch an example of a scatterplot that shows two variables with a strong association but a weak correlation?
http://mrsgallagher.pbworks.com/w/page/21762586/AP%20Stats%20-%20Chapter%207 (go to that link, good example there)
