Update insertion_sort_exercise.md

Author: dhavalsays

algorithms/4_InsertionSort/insertion_sort_exercise.md

@@ -2,7 +2,7 @@
 
 Compute the running median of a sequence of numbers. That is, given a stream of numbers, print out the median of the list so far on each new element.
 
-Recall that the median of an even-numbered list is the average of the two middle numbers.
+Recall that the median of an even-numbered list is the average of the two middle numbers in a *sorted list*.
 
 For example, given the sequence `[2, 1, 5, 7, 2, 0, 5]`, your algorithm should print out: