Scatterplot
Correlation
Least-Squares Regression
Residuals & Outliers
100
What is a scatterplot?
a type of graph used to represent the relationship between two variables
100
What does a correlation measure?
Strength and Direction of a relationship
100
True or False: The least regression line always passes through the point
True.
100
How can you tell if a point is an outlier?
It lies far away from the overall pattern.
200
What are the two types of variables used in a scatterplot?
Response, explanatory
200
Will r go up or down if you add a point that does not follow the trend?
Down.
200
What does it mean if a point lies exactly on the regression line?
The residual is zero
200
What is the formula for LSRL?
y^ = a + bx
300
What are the four components to describe a scatterplot?
Direction, Unusual features, Form, Strength
300
If r=0.55, describe the correlation.
Positive, Moderate
300
The least squares regression line minimizes the ___of
the squared residuals.
Sum
300
___ Outliers--> Tilt the line
___ Outliers--> Shift line up or down
Horizontal
Vertical
400
Draw a strong, positive, linear relationship.
400
What does it mean when the residuals are randomly scattered with no pattern?
The linear model is appropriate
400
What pattern in a residual plot suggest a linear model is NOT appropriate?
A curved or systematic pattern (U-shape or inverted U)
500
Why does correlation not imply causation?
Correlation indicates a statistical association between the two variables, causation means change in one variable directly causes a change in the other
500
What is an influential point in regression analysis?
A point that significantly changes the slope or intercept of the regression line when removed.
500
What is a residual in a regression model?
The difference between the observed vale and the expected value.