Two-Way Tables
What type of relative frequency compares part of the sample to the overall total?
Joint relative frequency.
What graph displays the relationship between two quantitative variables?
Scatterplot.
What does correlation measure?
Strength and direction of a linear relationship.
What is a residual?
Observed value - predicted value.
What is the purpose of a least-squares regression line?
To predict values and minimize residuals.
What type of relative frequency compares within a single group or category?
Conditional relative frequency.
What does a positive association mean?
As one variable increases, the other tends to increase.
What correlation value represents a strong positive relationship?
A value close to +1.
What does a positive residual mean?
The point is above the regression line.
What is the standard form of a regression equation?
ŷ = a + bx
Why can’t segmented bar graphs show joint relative frequencies?
Because they only show conditional frequencies.
What does a negative association mean?
As one variable increases, the other tends to decrease.
What correlation value represents little to no linear relationship?
A value close to 0.
What does a negative residual mean?
The point is below the regression line.
What does the slope in a regression equation represent?
The predicted change in y for every 1-unit increase in x.
What does a mosaic plot show that segmented bar graphs do not?
Different sample sizes using widths on the x-axis.
What does a strong association look like on a scatterplot?
Points closely follow a pattern or line.
Can correlation alone prove causation?
No.
What does random scatter in a residual plot suggest?
A linear model is appropriate.
Why might statisticians transform data before regression?
To make the relationship more linear.
If two categories have equal relative frequencies, what does that mean?
The percentages are the same even if the counts are different.
What type of relationship curves instead of forming a straight-line pattern?
Nonlinear relationship.
Can correlation alone determine if a relationship is linear?
No.
What does a curved pattern in a residual plot suggest?
A linear model is not appropriate.
What shows that a transformed model is better?
The residual plot has more random scatter.