The Median speed decreased by 9 mph after the bump was built.
Using the stem and leaf dataset :
Before :
- 19, 27, 31, 32, 36, 38, 41, 41, 43
Median = 1/2(n+1)th term
Median = 1/2(10)th = 5th term
Median = 36
After :
- 18, 22, 23, 26, 27, 28, 33, 33, 40
Median = 1/2(n+1)th term
Median = 1/2(10)th = 5th term
Median = 27
Difference = 36 - 27 = 9
The median speed decreased by 9 mph .