Statistics: Finding the Median: TEAS Practice Question with Answer & Explanation

Understanding the Median in Statistics

In the ATI TEAS 7 Math section, you will frequently encounter statistics questions involving the mean, median, mode, and range. To find the median, you are looking for the exact middle value of a data set. However, a common mistake students make is picking the number that appears in the middle of the list as it is currently written.

To correctly identify the median, you must follow these steps:

1. Arrange the Data in Ascending Order

The original set provided is: 18, 9, 21, 12, 7. Before doing anything else, you must rewrite these numbers from smallest to largest:

• 7, 9, 12, 18, 21

2. Identify the Middle Value

Since there are five numbers in this set (an odd number), there is a single clear middle value.

• 7 (1st)
• 9 (2nd)
• 12 (3rd) — This is the middle!
• 18 (4th)
• 21 (5th)

The median fluid intake for the patient is 12 ounces.

Why the Other Options Are Incorrect

• Choice A: 13. This might be the result of a calculation error if a student tried to find the mean (average) but divided incorrectly. (The actual mean is 13.4).
• Choice C: 15.5. This is a "distractor" value. Students might get this if they don't reorder the numbers and try to find the average of the two numbers currently in the "middle" slots of the unsorted list (21 and 12).
• Choice D: 16. This is another distractor that does not correlate to the standard statistical measures of this specific data set.

TEAS Tip: Handling Even vs. Odd Data Sets

• Odd number of values: The median is the single middle number (as seen in this problem).
• Even number of values: If the set had six numbers (e.g., 7, 9, 12, 18, 21, 25), you would take the two middle numbers (12 and 18), add them together (30), and divide by 2 to get a median of 15.

Memory Trick: The "Median" in the Road

Think of the median strip on a highway or road. It is the physical divider that sits exactly in the middle of the lanes. Just like the road's median, the statistical median divides your data set perfectly in half.