The correct option is D Remains the same as that of the original set
Given, the median of a set of 11 distinct observations is 15.5.
Since, Median is the middle most term in given data, so if we have total 11 terms then middle most term is 6th term.
∴6th term =15.5
If each of the smallest 5 observations of the set are decreased by 3, then 6th term of the data still remains same.
Therefore, Median remains same as that of Original set.
Option D is correct.