Question 1

Which of the following best describes the association shown in the Kentucky Derby scatterplot (speed vs. years since 1874)?

Accepted Answer

There is a positive, approximately linear association with moderate strength and a few possible outliers.

Question 2

In a scatterplot, which feature is NOT one of the four main aspects used to describe the association?

Accepted Answer

Slope

Question 3

Suppose you calculate the correlation coefficient $$r$$ for a dataset and obtain $$r = -0.85. $$Which of the following is true?

Accepted Answer

$$r = -0.85$$ represents a strong negative linear association.

Question 4

Which of the following is a necessary condition for interpreting the correlation coefficient $$r$$?

Accepted Answer

Both variables must be quantitative.

Question 5

Given the formula for correlation coefficient $$r$$:

$$ r = \frac{\sum (z_x z_y)}{n-1} $$

What does the sign of $$r$$ indicate?

Accepted Answer

The direction of the linear association

Question 6

Which region in the second scatterplot (labeled 1, 2, 3, 4) contains points that make positive contributions to $$r$$?

Accepted Answer

Regions 1 and 3

Question 7

If you switch the explanatory and response variables in a correlation calculation, what happens to the value of $$r$$?

Accepted Answer

The value of $$r$$ remains the same.

Question 8

A researcher finds a strong positive correlation between ice cream sales and drowning incidents. Which of the following is the best explanation?

Accepted Answer

There is a lurking variable (such as temperature) causing both to increase.

Question 9

Which of the following statements about correlation is FALSE?

Accepted Answer

Correlation has units determined by the variables.

Question 10

Which of the following is the best interpretation of $$r = 0$$?

Accepted Answer

There is no linear association between the variables.

Question 11

A scatterplot shows a strong, positive, linear association with one outlier far above the main cluster. How might this outlier affect the correlation coefficient $$r$$?

Accepted Answer

It could inflate $$r$$, making the association appear stronger than it is.

Question 12

Which of the following is NOT a possible reason for an observed association between two variables?

Accepted Answer

Correlation always implies causation

Question 13

Which of the following best describes the strength of the association if $$|r| is $$close to 1?

Accepted Answer

The association is strong.

Question 14

Before interpreting the value of $$r$$, what should you always do?

Accepted Answer

Look at the scatterplot.

Question 15

Which of the following is a correct statement about the possible values of the correlation coefficient $$r$$?

Accepted Answer

$$-1 \leq r \leq 1$$

Scatterplots, Association, and Correlation: Study Notes

Guida di studio - Domande di pratica

Study guide - Flashcard