By Stan Gibilisco — McGraw-Hill Professional

Updated on Sep 12, 2011

Review the following concepts if necessary:

- Percentiles Help
- Quartiles and Deciles Help
- Intervals by Element Quantity Help
- Fixed Intervals Help
- Descriptive Measures Other Specifications Help

**Descriptive Measures Practice Test**

A good score is 8 correct.

- Suppose a large number of people take a test. The 3rd decile point is determined by
- finding the highest score representing the ''worst'' 20% or fewer papers; the 3rd decile is at the top of that set
- finding the highest score representing the ''worst'' 30% or fewer papers; the 3rd decile is at the top of that set
- finding the lowest score representing the ''best'' 20% or fewer papers; the 3rd decile is at the bottom of that set
- finding the lowest score representing the ''best'' 30% or fewer papers; the 3rd decile is at the bottom of that set

- Suppose many students take a 10-question quiz, and the mean turns out to be 7.22 answers correct. Suppose the standard deviation turns out to be 0.722. What is the coefficient of variation?
- We can't answer this unless we know how many people take the quiz.
- 0.1
- 10
- 100

- Suppose several students take a 10-question quiz. The worst score is 3 correct, and the best score is 10 correct. What is the range?
- We can't answer this unless we know how many people take the quiz.
- 3/7
- 7
- 7/3

- Suppose several students take a 10-question quiz. The worst score is 3 correct, and the best score is 10 correct. What is the 50th percentile?
- 7, which is equal to 10 – 3.
- 6.5, which is equal to (3 + 10)/2.
- 30
^{1/2}, which is equal to the square root of (3 × 10). - We can't answer this unless we know how many students receive each score.

- Imagine that you take a standardized test, and after you've finished you are told that you are at the 91st decile. This means
- 90 of the students taking the same test have scores higher than yours
- 90% of all the students taking the same test have scores higher than yours

90 of the students taking the same test have scores lower than yours

- nothing; there is no such thing as the 91st decile
- Table 4-11 shows the results of a hypothetical 10-question test given to a group of students. Where is the 1st quartile point?
- At the transition between scores of 1 and 2.
- At the transition between scores of 4 and 5.
- At the transition between scores of 6 and 7.
- It cannot be determined without more information.

- What is the range for the scores achieved by students in the scenario of Table 4-11?
- 5
- 8
- 10
- It cannot be determined without more information.

**Table 4-11 **Illustration for Practice Test Questions 6 through 9. Results of a hypothetical 10-question test taken by 128 students.

- What is the interquartile range of the scores in Table 4-11?
- 3
- 4
- 6
- It cannot be determined because it is ambiguous.

- Suppose, in the scenario shown by Table 4-11, Jim Q. is one of the students taking the test, and he gets a score of 6. In what interval is Jim Q. with respect to the class?
- The bottom 25%.
- The next-to-lowest 25%
- The next-to-highest 25%.
- It cannot be determined because it is ambiguous.

- Suppose you see a pie graph showing the results of a survey. The purpose of the survey is to determine the number and proportion of families in a certain city earning incomes in various ranges. Actual numbers are, for some reason, not indicated on this pie graph. But you see that one of the ranges has a ''slice'' with an apex (central) angle of 90°. From this, you can assume that the slice corresponds to
- the families whose earnings fall into the middle 25% of the income range
- 25% of the families surveyed
- 1/π of the families surveyed (π is the ratio of a circle's circumference to its diameter)
- the families whose earnings fall within the interquartile range

**Answers**

- b
- b
- c
- d
- d
- b
- b
- a
- b
- b

From Statistics Demystified: A Self-Teaching Guide. Copyright © 2004 by The McGraw-Hill Companies. All Rights Reserved.

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