Let 9 distinct observations are x1,x2,x3,x4,x5,x6,x7,x8, and x9 (Observations in ascending order) Since n=9, then median term =(
9+1
2
)th=5th term.
Given: Median of a set of 9 distinct observations is 20.5 ∴x5=20.5 Now, the last four observations are increased by 2. So, New observations are x1,x2,x3,x4,x5,2x6,2x7,2x8, and 2x9 n=9, then median term =(
9+1
2
)th=5th term. So, The median is 5th observation, which is remaining unchanged. ∴ There will be no change in the median.