ISEE Upper Level Quantitative : How to find median

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

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Example Questions

Example Question #573 : Isee Upper Level (Grades 9 12) Quantitative Reasoning

A data set has six known quantities and two unknown positive quantities, as follows:

It is known, however, that 

Which is the greater quantity?

(A) The mean of the data set 

(B) The median of the data set   

Possible Answers:

(A) and (B) are equal

(A) is greater

(B) is greater

It is impossible to determine which is greater from the information given

Correct answer:

It is impossible to determine which is greater from the information given

Explanation:

If , then the mean of the data set is the sum of the eight elements divided by eight:

The median of the data set, however, depends on the values of  and , as can be demonstrated using two cases.

Case 1: 

The data set is then 

and the median is the mean of the two middle values. Since both middle values are 35, the median is 35.

Case 2:  and 

The data set is then 

and the median is the mean of the two middle values. They are 25 and 35, so the median is 

In the first case, the median is greater than the mean; in the second case, the mean is greater than the median. Therefore, the information is insufficient.

Example Question #581 : Isee Upper Level (Grades 9 12) Quantitative Reasoning

A data set has six known quantities and two unknown quantities, as follows:

Which is the greater quantity?

(A) The median of the set if  and 

(B) The median of the set if  and 

Possible Answers:

(A) is greater

(B) is greater

(A) and (B) are equal

It is impossible to determine which is greater from the information given

Correct answer:

(A) and (B) are equal

Explanation:

The median of a data set with an even number of elements is the mean of the middle two numbers, assuming the elements are arranged in order; since the data set has eight elements, the median will be the mean of the fourth-lowest element and the fourth-highest element.

If  and , the data set becomes ; if  and , the data set becomes . In both data sets, the middle two elements are 25 and 35, making both medians equal to . The quantities are equal.

Note: You don't need to do the last step and actually find the median. As long as you know that the two medians are the same, you've answered the question!

Example Question #582 : Isee Upper Level (Grades 9 12) Quantitative Reasoning

Over each of the past seven days, Beth has driven the following number of miles:

If M is equal to the mode, N is equal to the median, and O is equal to the mean, what is the order of M, N, and O from smallest to largest?

Possible Answers:

Correct answer:

Explanation:

The first step is to reorder the set, , in order from smallest to largest. 

The mode (which occurs most often) is 3.3, so 

The median is the middle number in the set (which is 6.8, having 3 numbers to its right and 3 to its left in the ordered list), so 

The mean (or average) is , so 

Therefore, 

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