The marks obtained by 9 students in a class test are recorded below: 9, 8, 7, 5,7, 6, 8, 9 and 7. What is the median mark?

Analyze the question: We need the median of 9 marks. The median is the middle value once the data is arranged in order.

Concept:

• Arrange the data in ascending (or descending) order.
• If there are n values and n is odd, the median is the value at position (n + 1)/2.

Solution:

Given marks: 9, 8, 7, 5, 7, 6, 8, 9, 7 (that is 9 values)

Step 1: Arrange in ascending order:

5, 6, 7, 7, 7, 8, 8, 9, 9

Step 2: Find the position of the median:

Position = (9 + 1)/2 = 5th value

Step 3: Pick the 5th value:

1st = 5, 2nd = 6, 3rd = 7, 4th = 7, 5th = 7, 6th = 8, 7th = 8, 8th = 9, 9th = 9

Median = 7

Answer: A. 7

Tip: Always sort the data first. Many students pick the middle number of the unsorted list, which gives the wrong answer here (the unsorted middle is 7 by coincidence, but it won't always work). Also, count your values to check that you have the right n. For an odd n, the median is a value in the list, so options like 8.5 or 7.5 (which come from averaging two middle numbers) are usually distractors.