Module 6 Flashcards
A bivariate distribution is represented in most complete fashion by A) A straight line B) A scatter plot C) A Pearson r D) A line, whether curved or straight
B) A scatter plot
Which of the following would be most likely to show a negative correlation?
A) Reaction time and skill as a driver
B) Height and shoe size
C) Hours studied and exam grade
D) Weight of automobile and gas used per mile
A) Reaction time and skill as a driver
In the “world of real data,” we are least likely to find values of r that are
A) Negative
B) Very close to zero
C) Very close to 1.00
D) Either close to zero or very close to 1.00
C) Very close to 1.00
If r = .50 and SXSY = 90, then the covariance is equal to: A) +2 B) -0.50 C) +45 D) -180
C) +45
What is the principal weakness of the covariance?
A) The covariance is not a measure of linear association
B) The magnitude of the covariance is influenced by the presence of outliers
C) The covariance does not convey the direction of association
D) The magnitude of the covariance is influenced by a variable’s metric
D) The magnitude of the covariance is influenced by a variable’s metric,
To learn how well we can predict Y from knowledge of X, we calculate r and find it to be r = -1.16. From this, we know that:
A) High values of X are predictive of low values of Y
B) The scores in Y are generally low
C) The mean of X is higher than the mean of Y
D) We have made a mistake in calculation
D) We made a mistake in calculation
If r = -1.00
A) X is of no use in predicting Y
B) Values of Y can be predicted from values of X without error
C) Either the X scores or the Y scores must be negative
D) The relationship becomes difficult to interpret
B) Values of Y can be predicted from values of X without error
In a scatter diagram, if one of the data points does not fall on the straight line of best fit, r cannot be A) 0 B) ±1 C) Positive D) Negative
B) ±1
Fifty students take a 100-item true-false test. Every student attempts every item. For each student, let X be the number of questions answered correctly and Y be the number not answered correctly. We would expect rXY to be A) +1.00 B) Zero C) -1.00 D) Between zero and -1.00
C) -1.00
If the standing in X is of no help in predicting standing in Y, then r is A) 0 B) -1.00 C) Less than -1.00 D) Indeterminate
A) 0
Which value of r indicates the least amount of relationship? A) 0.08 B) -0.12 C) 0.85 D) -0.98
A) 0.08
Which value of r indicates the strongest degree of relationship? A) 0.32 B) -0.79 C) 0.21 D) -0.91
D) -0.91
Consider the following data:
X Y 2 7 2 2 5 3
∑(X - x̄)(Y - ȳ) = A) +7 B) -2 C) +3 D) -3
D) -3
In the defining formula for Pearson r (Formula 7.2), the quantity that determines whether r will be negative or positive is A) n B) ∑(X - x̄)(Y - ȳ) C) SX and SY D) The combination of all these values
B) ∑(X - x̄)(Y - ȳ)
One hundred subjects are classified according to their standing in X and in Y. The classification looks like this:
below x̄ above x̄
above ȳ 18 32
below ȳ 35 15
From this information, we would say that A) r is large and positive B) r is moderate and positive C) r is zero D) r is negative
B) r is moderate and positive
It is possible to compute a correlation coefficient if we have
A) A pair of scores for one individual
B) A set of scores for a group of individuals
C) Two sets of scores for the same group of individuals
D) A set of scores for one group of individuals and a set of scores for another group of individuals
C) Two sets of scores for the same group of individuals
To begin calculating r by the raw score method, how should X and Y scores be ordered?
A) The X scores should be put in order of magnitude
B) Both X and Y scores should be put in order of magnitude
C) The pairs of X and Y scores may be in any order as long as the proper pairing is retained.
D) Any of the above procedures will be satisfactory
C) The pairs of X and Y scores may be in any order as long as the proper pairing is retained.
Consider these two pairs of scores:
X Y 2 3 4 5
For these data, the value of ∑XY is A) 14 B) 22 C) 23 D) 26
D) 26
Consider these two pairs of scores:
X Y 3 4 1 2
For these data, the value of ∑XY - (∑X)(Y)/n is A) +3 B) -4 C) +2 D) -2
C) +2
A causal relationship between X and Y can be inferred
A) Only on grounds that go beyond the simple showing of a degree of relationship
B) Any time r is other than zero
C) Only for positive values of r
D) Only for values of r which are near 1.00
A) Only on grounds that go beyond the simple showing of a degree of relationship
In a group of children of ages 7 to 13, strength of grip was correlated with number of correct answers on an arithmetic test. We would expect this correlation to be A) Strongly negative B) Moderately negative C) Close to zero D) Moderately positive
D) Moderately positive
Which statement is true?
A) Fundamentally, a degree of association between two variables signifies a causal relationship between them
B) Fundamentally, a causal relationship between two variables results in a degree of association between them
C) Both (A) and (B) are true
D) Neither (A) nor (B) are true
B) Fundamentally, a causal relationship between two variables results in a degree of association between them
In one study of auto drivers, it was found that a lower frequency of accidents was associated with more years of experience and with greater age of the driver. In explaining this finding, it might be that
A) Experience is the important factor in having fewer accidents, and age is not
B) Age is the important factor, and experience is not
C) Both age and experience make a contribution to infrequency of accidents
D) Any of the above could be true
D) Any of the above could be true
Which of the following explains why poor grades and poor attendance often go together?
A) Poor grades might in part result in poor attendance
B) Poor attendance might result in poor grades
C) A third factor may be responsible
D) All of the above might be true
D) All of the above might be true
