Deck 4: Normal Distributions

Question 1

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

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

Answer 1

33

Question 2

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

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.

Answer 2

The scores on it tend to form a standard normal distribution.

Question 3

A leptokurtic distribution of a variable:

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

Answer 3

has a steep peak.

Question 4

A z-score is:

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 5

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?

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

Question 6

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

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

Question 7

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

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

Question 8

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

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

Question 9

In the standard normal distribution:

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

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?

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

Question 11

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

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

Question 12

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

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