Calculating range

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GMAT Quantitative › Calculating range

Questions 1 - 10
1

A large group of students is given a standardized test. The following information is given about the scores:

Mean: 73.8

Standard deviation: 6.3

Median: 71

25th percentile: 61

75th percentile: 86

Highest score: 100

Lowest score: 12

What is the interquartile range of the tests?

More information about the scores is needed.

Explanation

The interquartile range of a data set is the difference between the 75th and 25th percentiles:

All other given information is extraneous to the problem.

2

Below is the stem-and-leaf display of a set of test scores.

What is the interquartile range of these test scores?

Explanation

The numbers in the "stem" of this display represent tens digits of the test scores, and the numbers in the "leaves" represent the units digits. This stem-and-leaf display represents twenty scores.

The interquartile range is the difference of the third and first quartiles.

The third quartile is the median of the upper half, or the upper ten scores. This is the arithmetic mean of the fifth- and sixth-highest scores. These scores are 73 and 69, so the mean is .

The first quartile is the median of the lower half, or the lower ten scores. This is the arithmetic mean of the fifth- and sixth-lowest scores. Both of these scores are the same, however - 57.

The interquartile range is therefore the difference of these numbers:

3

Consider the data set .

What is its midrange?

Explanation

The midrange of a data set is the arithmetic mean of its greatest element and least element. Here, those elements are and , so we can find the midrange as follows:

4

Find the range of the following data set:

Explanation

Find the range of the following data set:

Range is as simple as finding the diffference between the largest and smallest terms in a set. So, let's find our largest and smallest terms.

Largest: 989

Smallest: 2

Next, let's calculate the range:

So our answer should be 987

5

Find the range of the following set of numbers:

Explanation

To find range, subtract the smallest number from the largest number. Thus,

6

Find the range of the following set of numbers.

1,1,2,7,8,10,11

Explanation

To find the range, you m ust subtract the smallest number from the largest. Thus,

7

What is the range for the following data set:

Explanation

The range is the highest value number minus the lowest value number in a sorted data set:

We need to sort the data set:

8

.

Give the midrange of the set .

Explanation

The midrange of a set is the arithmetic mean of the greatest and least values, which here are and . This makes the midrange .

9

Below is the stem-and-leaf display of a set of test scores.

What is the range of this set of scores?

Explanation

The range of a data set is the difference of the highest and lowest scores,

The numbers in the "stem" of this display represent tens digits of the test scores, and the numbers in the "leaves" represent the units digits. The highest and lowest scores represented are 87 and 42, so the range is their difference: .

10

Calculate the range of the following set of data:

Explanation

The range of a set of data is the difference between its highest value and its lowest value, as this describes the range of values spanned by the set. A quick way to calculate the range is to locate the lowest value in the set and subtract it from the highest value, but let's arrange the set in increasing order to visualize the problem first:

Now we can see that the lowest value in the set is 9, and the highest value in the set is 27, so the range of the set is:

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