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Exam 15: Correlation

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Question 21

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A set of n = 15 pairs of scores (X and Y values) produces a correlation of r = 0.40.If each of the X values is multiplied by 2 and the correlation is computed for the new scores, what value will be obtained for the new correlation?

A) r = 0.20
B) r = 0.40
C) r = 0.80
D) cannot be determined without knowing all the X and Y scores

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Question 22

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A Pearson correlation of r = -0.90 indicates that the data points are clustered close to a line that slopes down to the right.

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Question 23

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The Pearson and the Spearman correlations are both computed for the same set of data.If the Pearson correlation is r = +1.00, then what can you conclude about the Spearman correlation?

A correlation of r = -0.95 means that there is essentially no consistent relationship between X and Y.

For a positive correlation, decreases in X tend to be accompanied by decreases in Y.

Suppose that there is a correlation of r = -0.41 between the amount of time that each student reports studying for an exam and the student's grade on the exam.This correlation would mean that there is a tendency for people who study more to get better grades.

A set of n = 5 pairs of X and Y values has SS_X = 16, SS_Y = 4 and SP = 2.For these data, the Pearson correlation is _____.

A Spearman correlation of r_S = 0.45 is computed for a sample of n = 22 people.This is sufficient to conclude that there is a real (non-zero) correlation in the population.

The sign of the correlation (+/-) is generally meaningless for the point-biserial correlation and the phi-coefficient.

A negative correlation means that decreases in the X variable tend to be accompanied by decreases in the Y variable.

The effect size for the data from an independent-measures t test can be measured by r² which is the percentage of variance accounted for.Which of the following also produces the value for r²?

The scatter plot for a set of X and Y values shows the data points clustered in a nearly perfect circle.For these data, what is the most likely value for the Pearson correlation?

If the following seven scores are ranked from smallest (#1) to largest, then what rank should be assigned to a score of X = 6? Scores: 1, 1, 3, 6, 6, 6, 9

For a two-tailed hypothesis test evaluating the significance of a Pearson correlation, the null hypothesis states that the correlation for the population is zero.

If the Pearson correlation is calculated for a sample of n = 20 individuals, what value for df should be used to determine whether or not the correlation is significant?

For a set of n = 10 pairs of scores with $\Sigma$ X = 10, $\Sigma$ Y = 40, and $\Sigma$ XY = 50, the sum of products of deviation is SP = 10.

The numerical value for a correlation _____.

The Spearman correlation can be +1.00 or -1.00 even when there is no linear relationship between the two variables.

A Pearson correlation is computed for a sample of n = 18 pairs of X and Y values.What correlations are statistically significant with α = .05, two tails.

If you measured hearing acuity and age for a group of people who are 50 to 90 years old, you should obtain a negative correlation between the two variables.