Question 1

Which of the following statements best describes the meaning of correlation?

Accepted Answer

Correlation is the co-variation or co-relation between two variables that change together, usually scale variables.

Question 2

A researcher finds a correlation coefficient of $$r = -0.85$$ between hours spent watching TV and exam scores. What does this indicate?

Accepted Answer

There is a strong negative relationship between hours spent watching TV and exam scores.

Question 3

Which of the following correlation coefficients represents the strongest relationship?

Accepted Answer

$$r = -0.74$$

Question 4

Why is it important to remember that 'correlation is NOT causation'?

Accepted Answer

Because a third variable may be responsible for the observed relationship.

Question 5

Given the formula for the Pearson correlation coefficient: $$r = \frac{\sum{(X - M_x)(Y - M_y)}}{\sqrt{(SS_x)(SS_y)}}$$, what does the denominator represent?

Accepted Answer

The square root of the product of the sums of squares for each variable.

Question 6

A perfect positive correlation is represented by which value?

Accepted Answer

$$r = 1.00$$

Question 7

If a scatterplot shows that as the number of absences increases, exam grades decrease, what type of correlation is this?

Accepted Answer

Negative correlation

Question 8

Which of the following is a limitation of correlation analysis?

Accepted Answer

It cannot account for invisible third variables that may influence the relationship.

Question 9

What is the main purpose of starting with a scatterplot when analyzing correlation?

Accepted Answer

To visually inspect the linear relationship between two variables.

Question 10

In psychometrics, why is correlation used to assess reliability?

Accepted Answer

Because reliability refers to the consistency of a measure, which can be evaluated by correlating repeated measurements.

Question 11

Which of the following best describes split-half reliability?

Accepted Answer

It correlates odd-numbered items with even-numbered items on the same test.

Question 12

What does coefficient alpha ($$\alpha$$), also known as Cronbach's alpha, estimate?

Accepted Answer

The average of all possible split-half correlations, providing an estimate of a test's reliability.

Question 13

How is validity typically assessed using correlation?

Accepted Answer

By correlating a new measure with existing measures known to assess the variable of interest.

Question 14

What is partial correlation used for?

Accepted Answer

To measure the association between two variables while mathematically eliminating the influence of a third variable.

Question 15

Which step in correlation hypothesis testing involves stating the null and research hypotheses?

Accepted Answer

Step 2

Question 16

A study finds a correlation of $$r = 0.91$$ between ice cream consumption and drowning deaths. What is the most appropriate interpretation?

Accepted Answer

There is a strong association, but correlation does not imply causation; a third variable may be responsible.

Question 17

Which symbol is used for the Pearson correlation coefficient when referring to a population parameter?

Accepted Answer

$$\rho$$

Question 18

If a correlation coefficient is $$r = 0.10$$, how would you describe the strength of the relationship?

Accepted Answer

Small

Question 19

Which of the following is a correct step in calculating the Pearson correlation coefficient?

Accepted Answer

Divide the sum of the products of the deviations by the square root of the products of the sums of squares for each variable.

Question 20

Why is establishing validity usually more difficult than establishing reliability in psychometric tests?

Accepted Answer

Because reliability only requires consistency, while validity requires evidence that the test measures what it is intended to measure.

Chapter 15: Correlation – Statistical Relationships Between Variables

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