Unit 2 Review of Concepts
Be sure you feel comfortable with all of the following concepts. These are the “big ideas” of Unit 3!
Interpretations:
Interpret r2 correctly. (Know the sentence)
Interpret slope correctly. (Know the sentence)
Interpret y-intercept correctly. (Know the sentence)
Interpret standard deviation of the residuals, s. (Know the sentence)
Interpret correlation, r: it tells strength and direction of the association between the two variables.
r is always between -1 and 1.
If r is close to -1 or 1, there is a strong association.
If r is close to 0, there is a weak association.
r does NOT assess the form of an association.
Correlation is a standardized value and does NOT have units attached to it.
Correlation is not affected by adding/subtracting or multiplying/dividing the scale(s) of the
variables.
Interpret a residual plot. A curved pattern means a linear model is not appropriate. A megaphone pattern
means to use caution when using the LSRL where residuals are large.
Do you KNOW….
That scatterplots are made with two quantitative variables. No categorical variables are used.
How to determine the explanatory and response variable from the context of the problem and which axis
each goes on.
How to determine the association from the context of the problem.
The definition of LSRL.
How to get the LSRL from summary statistics using formulas for slope and y intercept.
How to get the LSRL from reading computer output.
That the point (𝑥̅ , 𝑦%) is actually on the LSRL.
How to use the Least Squares Regression Line to make predictions.
How outliers affect LSRL, residuals, and correlation.
How to calculate and interpret a residual.
How r2 is related to r.