ISEE Upper Level Math : Data Analysis

Study concepts, example questions & explanations for ISEE Upper Level Math

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Example Questions

Example Question #6 : How To Find Median

Find the median in the following set of data:

 

\(\displaystyle \left \{ 2,3,4,1,2,4,3,7,3,4 \right \}\)

Possible Answers:

\(\displaystyle 2\)

\(\displaystyle 4\)

\(\displaystyle 1\)

\(\displaystyle 7\)

\(\displaystyle 3\)

Correct answer:

\(\displaystyle 3\)

Explanation:

In order to find the median, the data must first be ordered. So we should write:

 

\(\displaystyle \left \{ 1,2,2,3,3,3,4,4,4,7 \right \}\)

 

When the number of values is even, the median is the mean of the two middle values. In this problem we have \(\displaystyle 10\) values, so the median would be the mean of the \(\displaystyle 5th\) and \(\displaystyle 6th\) values:

 

\(\displaystyle Median=\frac{3+3}{2}=3\)

Example Question #7 : How To Find Median

If \(\displaystyle t\) is a real number, find the median in the following set of data in terms of \(\displaystyle t\).

 

\(\displaystyle \left \{ t,t+4,t+2,t+5,t+1,t+8 \right \}\)

Possible Answers:

\(\displaystyle t+4\)

\(\displaystyle t+3\)

\(\displaystyle t+1\)

\(\displaystyle t+2\)

\(\displaystyle t-2\)

Correct answer:

\(\displaystyle t+3\)

Explanation:

The data should first be ordered:

 

\(\displaystyle \left \{ t, t+1, t+2, t+4, t+5, t+8 \right \}\)

 

When the number of values is even, the median is the mean of the two middle values. So in this problem we need to find the mean of the \(\displaystyle 3th\) and \(\displaystyle 4th\) values:

 

\(\displaystyle Median=\frac{(t+2)+(t+4)}{2}=\frac{2t+6}{2}=t+3\)

Example Question #92 : Statistics

The heights of the members of a basketball team are \(\displaystyle 64,78,76,80,82,83,75,x\) inches. The mean of the heights is \(\displaystyle 78\ in\). Give the median of the heights.

Possible Answers:

\(\displaystyle 79\ in\)

\(\displaystyle 80\ in\)

\(\displaystyle 82\ in\)

\(\displaystyle 83\ in\)

\(\displaystyle 81\ in\)

Correct answer:

\(\displaystyle 79\ in\)

Explanation:

The mean is the sum of the data values divided by the number of values or as a formula we have:

 

\(\displaystyle \bar{x}=\frac{1}{n}\sum_{i=1}^{n}x_{i}\)

 

Where:

 

\(\displaystyle \bar{x}\) is the mean of a data set, \(\displaystyle \sum\) indicates the sum of the data values \(\displaystyle x_{i}\) and \(\displaystyle n\) is the number of data values. So we can write:

 

\(\displaystyle \bar{x}=\frac{1}{n}\sum_{i=1}^{n}x_{i}=\frac{(64+78+76+80+82+83+75+x)}{8}\)

\(\displaystyle \Rightarrow \bar{x}=\frac{538+x}{8}=78\Rightarrow 538+x=78\times 8\)

\(\displaystyle \Rightarrow 538+x=624\Rightarrow x=624-538=86\ in\)

 

In order to find the median, the data must first be ordered:

 

\(\displaystyle \left \{ 64,75,76,78,80,82,83,86 \right \}\)

 

Since the number of values is even, the median is the mean of the two middle values. So we get:

 

\(\displaystyle Median=\frac{78+80}{2}=79\ in\)

 

 

Example Question #31 : Data Analysis And Probability

Give the median of the frequency distribution shown in the following table:

 

     \(\displaystyle \begin{matrix} Data \ Value & Frequency \\ 120 & 7\\ 142& 3\\ 160& 4\\ 174& 6 \end{matrix}\)

Possible Answers:

\(\displaystyle 150\)

\(\displaystyle 142\)

\(\displaystyle 144\)

 

\(\displaystyle 151\)

\(\displaystyle 138\)

Correct answer:

\(\displaystyle 151\)

Explanation:

There are \(\displaystyle 7+3+4+6=20\) data values altogether. When the number of values is even, the median is the mean of the two middle values. So in this problem the median is the mean of the \(\displaystyle 10th\) and \(\displaystyle 11th\) largest values. So we can write:

 

\(\displaystyle 10th\ largest \ value=142\)

\(\displaystyle 11th\ largest \ value=160\)

 

So:

 

\(\displaystyle Median=\frac{142+160}{2}=151\)

Example Question #31 : Data Analysis And Probability

Consider the data set 

\(\displaystyle \left \{ 24,61, 27, 57, 34, 37, 63, 50, N\right \}\).

For what value(s) of \(\displaystyle N\) would this set have median \(\displaystyle 50\)?

Possible Answers:

Any number greater than or equal to \(\displaystyle 50\)

Any number except \(\displaystyle 50\)

Any number less than or equal to \(\displaystyle 50\)

Any number less than \(\displaystyle 50\)

Any number greater than \(\displaystyle 50\)

Correct answer:

Any number greater than or equal to \(\displaystyle 50\)

Explanation:

Arrange the eight known values from least to greatest.

\(\displaystyle \left \{ 24, 27, 34, 37, 50, 57,61, 63\right \}\)

For \(\displaystyle 50\) to be the median of the nine elements, it muct be the fifth-greatest, This happens if \(\displaystyle N \geq 50\).

Example Question #581 : Isee Upper Level (Grades 9 12) Mathematics Achievement

Consider the data set: \(\displaystyle \left \{ 12, 15, 18, 20, 20, 21, 23, 26, N\right \}\)

where \(\displaystyle N\) is not known.

What are the possible values of the median of this set?

Possible Answers:

\(\displaystyle 20\textrm{ or }21\)

\(\displaystyle 18 \textrm{ or }20\)

\(\displaystyle 18, 20,\textrm{ or }21\)

\(\displaystyle 20\)

Correct answer:

\(\displaystyle 20\)

Explanation:

The median of this nine-element set is its fifth-highest element. Of the eight known elements, the fourth-highest and fifth-highest elements are both 20. Regardless of the value of \(\displaystyle N\), 20 is the fifth-highest element of the nine.

Example Question #11 : How To Find Median

Examine this stem-and-leaf display for a set of data:

\(\displaystyle \left.\begin{matrix} 4\\ 5\\ 6\\ 7\\ 8 \end{matrix}\right|\begin{matrix} \textrm{7 9}\; \; \; \; \; \; \; \; \; \; \;\; \; \; \; \; \; \; \; \; \; \; \; \;\\ \textrm{4 4 7 7}\; \; \; \; \; \; \; \; \; \; \;\; \; \; \; \; \; \; \\ \textrm{0 1 2 2 4 5 5 8 8 9}\\ \textrm{3 5 5 8}\; \; \; \; \; \; \; \; \; \; \;\; \; \; \; \; \; \; \\ \textrm{4 7}\; \; \; \; \; \; \; \; \; \; \;\; \; \; \; \; \; \; \; \; \; \; \; \; \end{matrix}\)

What is the median of this data set?

Possible Answers:

\(\displaystyle 67\)

\(\displaystyle 64\)

\(\displaystyle 64.5\)

\(\displaystyle 65\)

Correct answer:

\(\displaystyle 64.5\)

Explanation:

The "stem" of this data set represents the tens digits of the data values; the "leaves" represent the units digits. 

There are 22 elements, so the median is the arithmetic mean of the eleventh- and twelfth-highest elements, which are 64 and 65, the middle two "leaves". Their mean is \(\displaystyle \left (64 + 65 \right )\div 2 = 64.5\).

Example Question #12 : How To Find Median

Determine the median of the following seven test scores:

\(\displaystyle 88, 93, 79, 95, 80, 81, 93\)

Possible Answers:

\(\displaystyle 87\)

\(\displaystyle 95\)

\(\displaystyle 79\)

\(\displaystyle 93\)

\(\displaystyle 88\)

Correct answer:

\(\displaystyle 88\)

Explanation:

To determine the median of a set of numbers, you first need to order them from least to greatest:

\(\displaystyle 79, 80, 81, 88, 93, 93, 95\)

Since there is an odd number of scores, the median is the score that falls exactly in the middle of the new list. Thus, the median is 88.

Example Question #33 : Data Analysis And Probability

Determine the median of the following set of numbers:

\(\displaystyle 55, 34, 27, 36, 44, 51\)

Possible Answers:

\(\displaystyle 28\)

\(\displaystyle 36\)

\(\displaystyle 44\)

\(\displaystyle 40\)

\(\displaystyle 41\)

Correct answer:

\(\displaystyle 40\)

Explanation:

To determine the median of a set of numbers, you first need to order them from least to greatest:

\(\displaystyle 27, 34, 36, 44, 51, 55\)

Since there is an even amount of numbers, the median is determined by finding the average of the two numbers in the middle - 36 and 44.

\(\displaystyle 36+44 = 80 \div 2 = 40\)

 

Thus, the median is 40.

Example Question #13 : How To Find Median

Find the median of the following numbers:

\(\displaystyle 2,7,14,4,3\)

Possible Answers:

\(\displaystyle 7\)

\(\displaystyle 4\)

\(\displaystyle 6\)

\(\displaystyle 5\)

Correct answer:

\(\displaystyle 4\)

Explanation:

The median is the center number when the data points are listed in ascending or descending order. To find the median, reorder the values in numerical order:

\(\displaystyle 2,3,4,7,14\)

In this problem, the middle number, or median, is the third number, which is \(\displaystyle 4.\)

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