Question 1

Approximately what percentage of scores fall within one standard deviation of the mean?

Accepted Answer

A)   16
B)   34
C)   68
D)   98 C

Question 2

Lucille took the same exam, but received a 78 on it. What was her approximate percentile rank?

Accepted Answer

A)   78th
B)   16th
C)   58th
D)   84th B

Question 3

A leptokurtic distribution of a variable:

Accepted Answer

A)   is bell-shaped.
B)   is totally flat.
C)   has a steep peak.
D)   is not symmetrical. C

Question 4

When statisticians refer to the distribution of a variable as "skewed," they mean that a frequency polygon for the variable:

Accepted Answer

A)   would not be bell-shaped.
B)   would contain one or more outliers.
C)   would not be symmetrical
D)   all of the above

Question 5

A z-score is:

Accepted Answer

A)   the highest value that a variable can assume.
B)   the value of a variable that falls at +3 standard deviations from the mean.
C)   a raw score expressed in units of standard deviation.
D)   another name for an outlier.

Question 6

If the research sample contained 500 students, approximately how many had 21 or fewer friends?

Accepted Answer

A)   7
B)   467
C)   21
D)   33

Question 7

One hundred students took a statistics mid-term exam. The scores formed a normal distribution with a mean of 84 and a standard deviation of 6. Elice's grade was a 92. What was her approximate percentile rank?

Accepted Answer

A)   91st
B)   9th
C)   59th
D)   84th

Question 8

In a research sample of high school students, the variable "number of MySpace friends" formed a normal distribution with a mean of 45 and a standard deviation of 16. Valentina had 53 friends. What was her approximate percentile rank?

Accepted Answer

A)   31st
B)   53rd
C)   69th
D)   49th

Question 9

In the standard normal distribution:

Accepted Answer

A)   the curve is symmetrical
B)   the mean, the median, and the mode all occur at the same point.
C)   the curve approaches, but does not touch the x-axis.
D)   all of the above

Question 10

What does it mean when we say that a measurement instrument such as the SAT is a standardized test?

Accepted Answer

A)   The scores on it tend to form a standard normal distribution.
B)   Everyone receives about the same score on the test.
C)   The test provides a valid measurement of some variable.
D)   The test always contains the same questions in the same sequence.

Question 11

Approximately what percentage of scores of a normal distribution fall below -2 standard deviations?

Accepted Answer

A)   48%
B)   98%
C)   2%
D)   16%

Question 12

Which of the following z-scores would fall at the lowest percentile?

Accepted Answer

A)   2.00
B)   0.00
C)   -1.35
D)   1.35

Exam 4: Normal Distributions