The coefficient of determination

Question 1

	a.	Is a measure of the amount of variability in one variable that is shared by the other.
	b.	Is the square root of the correlation coefficient.
	c.	Indicates whether the correlation coefficient is significant.
	d.	Is the square root of the variance.

Question 2

Imagine a researcher wanted to investigate whether there was a significant correlation between IQ and annual income, but she had reason to believe that work ethic would influence both of these variables. What should she do?

	a.	Conduct a partial correlation to look at the relationship between work ethic and annual income partialling out the effect of IQ.
	b.	Conduct a semi-partial correlation to look at the relationship between IQ and work ethic while partialling out the effect of annual income.
	c.	Conduct a partial correlation to look at the relationship between IQ and annual income while partialling out the effect of work ethic.
	d.	Conduct a semi-partial correlation to look at the relationship between IQ and annual income while partialling out the effect of work ethic.

Question 3

Looking at the table below, which variables were the most strongly correlated?

	a.	None of the correlations are significant.
	b.	Work ethic and annual income.
	c.	Work ethic and IQ.
	d.	Annual income and IQ.

Question 4

	a.	It is not appropriate to use Pearson's correlation because it assumes a linear relationship between variables.
	b.	Transforming the data will not help.
	c.	Pearson's correlation can be used in the same way as it is for linear relationships.
	d.	You can use Pearson's correlation; you just need to remember that a curve indicates that the variables are not linearly related.

Question 5

A Pearson's correlation of -.71 was found between number of hours spent at work and energy levels in a sample of 300 participants. Which of the following conclusions can be drawn from this finding?

	a.	The estimate of the correlation will be imprecise.
	b.	There was a strong negative relationship between the number of hours spent at work and energy levels.
	c.	Amount of time spent at work accounted for 71% of the variance in energy levels.
	d.	Spending more time at work caused participants to have less energy.

Question 6

Which of the following statements about Pearson's correlation coefficient is not true?

	a.	It cannot be used with binary variables (those taking on a value of 0 or 1).
	b.	It can be used as an effect size measure.
	c.	It varies between -1 and +1.
	d.	It can be used on ranked data.

Question 7

	a.	The significance of the correlation coefficient.
	b.	All of these.
	c.	The +/- sign of the correlation coefficient.
	d.	The magnitude of the correlation coefficient.

Question 8

	a.	There is no unique variance.
	b.	The variables are independent.
	c.	They share variance.
	d.	The relationship is weak.

Question 9

Which correlation coefficient would you use to look at the correlation between gender and time spent on the phone talking to your mother?

	a.	The point-biserial correlation coefficient, r_pb.
	b.	The biserial correlation coefficient, r_b.
	c.	Kendall's correlation coefficient, τ.
	d.	Pearson's correlation coefficient, r.

Question 10

The relationship between two variables partialling out the effect that a third variable has on one of those variables can be expressed using a:

The coefficient of determination

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