#39
Top 50 Mistake
Finding median without ordering data first
"The Middle Muddle"
The Mistake in Action
Find the median of: 7, 3, 9, 2, 5
Student writes: "There are 5 values, so median is the 3rd one = 9"
Why It Happens
Students see "middle value" and just pick the one in the middle position of the list as given. They skip the crucial first step of putting values in order.
The Fix
Always rewrite the data in order first — smallest to largest.
7, 3, 9, 2, 5 becomes 2, 3, 5, 7, 9
Now the middle (3rd) value is 5, not 9.
Memory trick: "ORDER before MIDDLE" — you can't find the middle of a queue if everyone's standing randomly!
Spot the Mistake
Can you identify where this student went wrong?
Data: 7, 3, 9, 2, 5
5 values, so median is the 3rd value
Median = 9
Click on the line that contains the error.
Related Topics
Learn more about the underlying maths: