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Statistics > Module 6 > Flashcards

Module 6 Flashcards

1
Q 
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
A

B) A scatter plot

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2
Q

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

A) Reaction time and skill as a driver

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3
Q

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

A

C) Very close to 1.00

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4
Q 
If r = .50 and SXSY = 90, then the covariance is equal to:
A) +2
B) -0.50
C) +45
D) -180
A

C) +45

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5
Q

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

A

D) The magnitude of the covariance is influenced by a variable’s metric,

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6
Q

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

A

D) We made a mistake in calculation

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7
Q

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

A

B) Values of Y can be predicted from values of X without error

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8
Q 
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
A

B) ±1

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9
Q 
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
A

C) -1.00

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10
Q 
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

A) 0

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11
Q 
Which value of r indicates the least amount of relationship?
A) 0.08
B) -0.12
C) 0.85
D) -0.98
A

A) 0.08

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12
Q 
Which value of r indicates the strongest degree of relationship?
A) 0.32
B) -0.79
C) 0.21
D) -0.91
A

D) -0.91

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13
Q

Consider the following data:

	X	Y
	2	7
	2	2
	5	3
∑(X - x̄)(Y - ȳ) =
A) +7
B) -2
C) +3
D) -3
A

D) -3

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14
Q 
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
A

B) ∑(X - x̄)(Y - ȳ)

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15
Q

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
A

B) r is moderate and positive

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16
Q

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

A

C) Two sets of scores for the same group of individuals

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17
Q

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

A

C) The pairs of X and Y scores may be in any order as long as the proper pairing is retained.

18
Q

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
A

D) 26

19
Q

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
A

C) +2

20
Q

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

A) Only on grounds that go beyond the simple showing of a degree of relationship

21
Q 
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
A

D) Moderately positive

22
Q

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

A

B) Fundamentally, a causal relationship between two variables results in a degree of association between them

23
Q

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

A

D) Any of the above could be true

24
Q

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

A

D) All of the above might be true

25
Q

When a curved line is the line of best fit to the points in a scatterplot, Pearson r will describe
A) How well the points hug the curved line
B) How well the points hug the best fitting straight line
C) How well the points hug a line intermediate between the curved line and the straight line
D) None of the above

A

B) How well the points hug the best fitting straight line

26
Q

If Pearson r is calculated for data that are curvilinearly related, it will
A) Properly reflect the degree of association
B) Overestimate the degree of association
C) Underestimate the degree of association
D) Overestimate or underestimate the degree of association, depending on the circumstances

A

C) Underestimate the degree of association

27
Q

In a given group, the correlation between height measured in feet and weight measured in pounds is +.68. Which of the following would alter the value of r?
A) Height is expressed in centimeters
B) Weight is expressed in kilograms
C) Neither of the above changes will affect r
D) Both of the above changes will affect r

A

C) Neither of the above changes will affect r

28
Q 
In working one correlation problem, X scores are recorded to the first decimal (e.g., 12.2, 13.7, etc.).  For convenience, the decimal is ignored (e.g., scores are treated as though they were 122, 137, etc.).  If the obtained value of r is +.30, what will the correct value be?
A) +0.30
B) Greater than +0.30
C) +0.03
D) -0.30
A

A) +0.30

29
Q 
Among a group of children, the correlation between test score in a science course and test score in an English course is +.45.  It is learned that each science test score is 5 points too high, so each score is corrected and r recomputed.  We expect that its value will be
A) Greater than +0.45
B) Less than +0.45
C) Change in an unpredictable way
D) Unchanged
A

D) Unchanged

30
Q 
Random sampling variation among values of r is greatest when
A) The units of measurement are large
B) Sx and Sy are large
C) n is small
D) The relationship is nonlinear
A

C) n is small

31
Q

The correlation coefficient is obtained between academic aptitude test score and academic achievement (a) among students in general and
(b) among honor students. Other things being equal, we expect
A) The two coefficients to be about the same
B) The first to be higher
C) The second to be higher
D) One to be negative, the other positive

A

B) The first to be higher

32
Q

We would expect the correlation between height and weight for the Woodside High basketball team to be _____ the correlation for the entire student body.
A) About the same as
B) Higher than
C) Lower than
D) The answer will depend on the degree of sampling variation

A

C) Lower than

33
Q 
A group of highly creative men and women are studied to determine the degree of relationship between creativity ratings and IQ scores.  For this group we would expect the correlation to be
A) Low
B) Moderate
C) High
D) Negative
A

A) Low

34
Q 
The correlation between IQ scores and graduate GPA for a sample of Ph.D. candidates in psychology is computed to be +.17.  The most likely explanation for such a low correlation is
A) A restriction of range
B) A sampling error
C) An unreliable IQ test
D) Lack of an appropriate causal agent
A

A) Restriction of range

35
Q 
The r between job aptitude scores and job success ratings is computed to be +.29.  Which of the following is the best guess as to the value for r had all, rather than just the best qualified, applicants been hired?
A) +0.29
B) +0.41
C) +0.1
D) -0.32
A

B) +0.41

36
Q 
In general, an increase of .10 points in the correlation coefficient has the greatest consequence for r = :
A) 0.80
B) 0.50
C) 0.20
D) 0.05
A

A) 0.80

37
Q 
In a study concerned with the relationship between X and Y, it is found that 9% of the variance in Y is associated with X.  Thus rXY must have been:
A) 0.09
B) 0.30
C) 0.81
D) 0.08
A

B) 0.30

38
Q 
An investigator obtains r = +.4 between peer ratings of sociability and scores on the Wilson Sociability Inventory, for which x̄ = 50 and S = 10.  The amount of sociability inventory variance associated with variation in peer ratings is:
A) 4
B) 50
C) 40
D) 16
A

D) 16

39
Q 
In one study, a correlation of -.49 is found between the number of hours of TV watched per week and high school GPA.  According to this study, \_\_\_\_\_ of the GPA variance is associated with TV watching.:
A) 14%
B) 24%
C) 49%
D) 70%
A

B) 24%

40
Q 
One way of interpreting the degree of association between two variables involves first doing something to the correlation coefficient.  It involves
A) Taking its square root
B) Multiplying it by two
C) Subtracting it from one
D) Squaring it
A

D) Squaring it

41
Q 
Fifty percent of Y variance is associated with variation in X when r is approximately:
A) 0.90
B) 0.70
C) 0.50
D) 0.25
A

B) 0.70

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