ISEE Upper Level Math : Median

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

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Example Questions

Example Question #1 : Median

The following are the scores from a math test in a given classroom. What is the median score?

\(\displaystyle \small \left \{ 70,89,67,77,92,83,68,75\right \}\)

Possible Answers:

\(\displaystyle 77.625\)

\(\displaystyle 75\)

\(\displaystyle 76\)

\(\displaystyle 77\)

\(\displaystyle 84.5\)

Correct answer:

\(\displaystyle 76\)

Explanation:

To find the median you need to arrange the values in numerical order.

Starting with this:

Rearrange to look like this:

\(\displaystyle \small \small \left \{ 67,68,70,75,77,83,89,92\right \}\)

If there are an odd number of values, the median is the middle value. In this case there are 8 values so the median is the average (or mean) of the two middle values.

\(\displaystyle \small (75+77)\div2=76\)

Example Question #21 : Data Analysis And Probability

The median of nine consecutive integers is 604. What is the greatest integer?

Possible Answers:

\(\displaystyle 610\)

\(\displaystyle 613\)

\(\displaystyle 608\)

\(\displaystyle 607\)

\(\displaystyle 612\)

Correct answer:

\(\displaystyle 608\)

Explanation:

The median of nine (an odd number) integers is the one in the middle when the numbers are arranged in ascending order; in this case, it is the fifth lowest. Since the nine integers are consecutive, the greatest integer is four more than the median, or \(\displaystyle 604 + 4 = 608\).

Example Question #1 : Median

The median of \(\displaystyle 11\) consecutive integers in a set of data is \(\displaystyle 28\). What is the smallest integer in the set of data?

Possible Answers:

\(\displaystyle 22\)

\(\displaystyle 25\)

\(\displaystyle 24\)

\(\displaystyle 23\)

\(\displaystyle 26\)

Correct answer:

\(\displaystyle 23\)

Explanation:

We know that the numbers should be arranged in ascending order to find the median. When the number of values is odd, the median is the single middle value. In this question we have \(\displaystyle 11\) consecutive integers with the median of \(\displaystyle 28\). So the median is the \(\displaystyle 6th\) number in the rearranged data set. Since the \(\displaystyle 11\) integers are consecutive, the smallest integer is five less than the median or it is equal to \(\displaystyle 28-5=23\).

Example Question #2 : How To Find Median

What is the median of the frequency distribution shown in the table:

 

     \(\displaystyle \begin{matrix} Data \ Value & Frequency \\ 12 & 4\\ 14& 7\\ 15& 3\\ 18& 2 \end{matrix}\)

Possible Answers:

\(\displaystyle 11\)

\(\displaystyle 15\)

\(\displaystyle 10\)

\(\displaystyle 12\)

\(\displaystyle 14\)

Correct answer:

\(\displaystyle 14\)

Explanation:

There are \(\displaystyle 4+7+3+2=16\) 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 \(\displaystyle 8th\) and \(\displaystyle 9th\) largest values. So we can write:

 

\(\displaystyle 8th\ largest \ value=14\)

\(\displaystyle 9th\ largest \ value=14\)

 

So:

 

\(\displaystyle Median=\frac{14+14}{2}=14\)

Example Question #5 : How To Find Median

Scores from a math test in a given classroom are as follows:

 

\(\displaystyle \left \{ 80, 84, 86, 66, 57, 69, 92, 90 \right \}\)

 

What is the median score?

Possible Answers:

\(\displaystyle 84\)

\(\displaystyle 80\)

\(\displaystyle 78\)

\(\displaystyle 82\)

\(\displaystyle 86\)

Correct answer:

\(\displaystyle 82\)

Explanation:

In order to find the median the data must first be ordered. So we have:

 

\(\displaystyle \left \{ 57,66,69,80,84,86,90,92 \right \}\)

 

In this problem the number of values is even. We know that when the number of values is even, the median is the mean of the two middle values. So we get:

 

\(\displaystyle Median=\frac{80+84}{2}=82\)

Example Question #6 : How To Find Median

Heights of a group of students in a high school are as follows (heights are given in \(\displaystyle cm\)):

 

\(\displaystyle \left \{ 176,180,181,182,168,174,169,188,165 \right \}\)

 

Find the median height.

Possible Answers:

\(\displaystyle 174cm\)

\(\displaystyle 180cm\)

\(\displaystyle 178cm\)

\(\displaystyle 176 cm\)

\(\displaystyle 172cm\)

Correct answer:

\(\displaystyle 176 cm\)

Explanation:

In order to find the median the data must first be ordered. So we have:

 

\(\displaystyle \left \{ 165,168,169,174,176,180,181,182,188 \right \}\)

 

When the number of values is odd, the median is the single middle value. In this problem we have nine values. So the median is th \(\displaystyle 5th\) value which is \(\displaystyle 176cm\).

Example Question #3 : 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:

\(\displaystyle 2\)

\(\displaystyle 3\)

\(\displaystyle 1\)

\(\displaystyle 7\)

\(\displaystyle 4\)

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 #32 : Data Analysis

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:

\(\displaystyle t+3\)

\(\displaystyle t+2\)

\(\displaystyle t+4\)

\(\displaystyle t-2\)

\(\displaystyle t+1\)

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 #9 : How To Find Median

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:

\(\displaystyle 81\ in\)

\(\displaystyle 83\ in\)

\(\displaystyle 80\ in\)

\(\displaystyle 79\ in\)

\(\displaystyle 82\ in\)

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 #33 : Data Analysis

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:

\(\displaystyle 138\)

\(\displaystyle 151\)

\(\displaystyle 142\)

\(\displaystyle 150\)

\(\displaystyle 144\)

 

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:

 

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

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