Module 3

Question 1

A measure of variability provides information about
A) The level of performance
B) Shape of the distribution
C) Individual differences
D) Kurtosis

Answer 1

C) Individual differences

Question 2

If the lowest score is 51 and the highest score is 92, the range is
A) 41
B) 41.1
C) 41.5
D) 42

Answer 2

A) 41

Question 3

Eliminating some scores from a point near the mean will
A) Increase the standard deviation
B) Not affect the standard deviation
C) Decrease the standard deviation
D) Affect the standard deviation in an unpredictable way

Answer 3

A) Increase the standard deviation

Question 4

Consider the two scores, 4 and 8. 
SS =
A) 8
B) 4
C) 0
D) cannot be determined without further information

Answer 4

A) 8

Question 5

SS/n is
A) The average deviation
B) The standard deviation
C) The variance
D) None of the above

Answer 5

The variance

Question 6

Which among the following groups of scores would show the least variability when measured by the standard deviation? (no computations necessary)
A) 1 4 5 6 9
B) 1 2 5 8 9
C) 61 65 65 65 69
D) 61 63 65 67 69

Answer 6

C) 61 65 65 65 69

Question 7

The mean score on a quiz is 7, and the standard deviation is 0.  This shows that
A) A calculation error has been made
B) The distribution is normal
C) The distribution is rectangular
D) All persons scored 7 on the quiz

Answer 7

D) All persons scored 7 on the quiz

Question 8

Computing the standard deviation directly from deviation scores is useful:
A) For understanding the nature of s
B) When the score have not yet been grouped into a frequency distribution
C) When n is large
D) When the original scores are whole numbers

Answer 8

A) For understanding the nature of s.

Question 9

For the two scores, 2 and 4, (∑X)² is
A) 2
B) 6
C) 20
D) 36

Answer 9

D) 36

Question 10

∑X² - (∑X)² / n is one formula for
A) s²
B) s
C) ∑(X -X)²
D) SS

Answer 10

D) SS

Question 11

At one stage of calculation, we have S = √(-36) . From this, we know
A) S=6
B) One or more scores must have been wrongly copied from the original set
C) We have made an error in computation
D) Either (B) or (C) has occurred

Answer 11

C) We have made an error in computation

Question 12

Which measure is not dependent on the value of each score?
A) Standard deviation
B) Variance
C) Range
D) None of the above

Answer 12

C) Range

Question 13

The properties of the standard deviation are most closely related to those of the
A) Mean
B) Median
C) Mode
D) Median and mode

Answer 13

A) Mean

Question 14

With larger sample size, we would expect which measure(s) also to be larger?
A) Standard deviation
B) Variance
C) Range
D) None of the above

Answer 14

C) Range

Question 15

If one score in a distribution is changed to another value, it is certain that
A) The range has changed
B) The variance has changed
C) The standard deviation has changed
D) Both standard deviation and variance have changed

Answer 15

D) Both standard deviation and variance have changed

Question 16

In a normal distribution, about 5% of the scores fall outside of the limits
A) X ± 0.5S
B) X ± 1S
C) X ± 1.5S
D) X ± 2S

Answer 16

D) X ± 2S

Question 17

A frequency distribution of observations is approximately normal with x̄ = 60 and S = 5.  The middle 95% of the cases will fall (approximately) between
A) 45 and 75
B) 47.5 and 72.5
C) 50 and 70
D) 55 and 65

Answer 17

C) 50 and 70

Question 18

A frequency distribution of scores is normal with a mean of 80 and a standard deviation of 9.  Roughly \_\_\_\_\_\_ of the cases fall between scores of 71 and 89.
A) Half
B) Two thirds
C) Almost all
D) 95%

Answer 18

B Two thirds

Question 19

In a normal distribution, we expect about what percent of scores to fall above a score three standard deviations below the mean (i.e., above x̄ - 3S)
A) More than 99%
B) 97.5%
C) 95%
D) 84%

Answer 19

A) More than 99%

Question 20

If performance is normally distributed, and grades of A are given to those who score at 1 standard deviation above the mean or better, we should expect about what proportion of students to earn an A?
A) 32%
B) 16%
C) 5%
D) 2.5%

Answer 20

B) 16%

Question 21

Given: n1 > n2 and s₁ > s₂.  You therefore know that:
A) x̄₁ > x̄₂
B) s(pooled) is closer to s₂ than s₁
C) S₁² > S₂²
D) s(pooled) is closer to s₁ than s₂

Answer 21

D) s(pooled) is closer to s₁ than s₂

Question 22

An effect size
A) Expresses the magnitude of a mean difference in standard deviation units
B) Is used for conveying peakedness of a distribution
C) Can be misinterpreted if the horizontal and vertical axes are not scaled comparably
D) Is large when a distribution is markedly skewed

Answer 22

A) Expresses the magnitude of a mean difference in standard deviation units

Question 23

According to Cohen (1988), an effect size of -.85 would be considered
A) Negligible
B) Small
C) Moderate
D) Large

Answer 23

D) Large

Question 24

Given:
n1 = 16, x̄1 = 35, S₁² = 16
n2 = 16, x̄2 = 27, S₂² = 16

S(pooled) =
A) 2
B) 4
C) 16
D) cannot be computed from these data

Answer 24

B) 4

Question 25

Given:
n1 = 16, x̄1 = 35, S₁² = 16
n2 = 16, x̄2 = 27, S₂² = 16

d =
A) +0.50
B) +2
C) +8
D) +16

Answer 25

B) +2

Question 26

Seniors at two universities take the Graduate Record Examination. Students from the first institution earn a mean of 520; those from the second, 505. The standard deviation of this test was 100. Would you say that seniors at the first institution seem to be
A) Much superior to those at the second
B) A little superior to those at the second
C) Different, but it’s hard to say without knowing the range
D) Normally distributed

Answer 26

B) A little superior to those at the second