Mean, median and mode
The "mean," or "arithmetic mean," is what is traditionally referred to as
"average." It is the only one of the measurements which requires
calculation.
The "median" is the middle point, or the middle number, among a
distribution of numbers.
The "mode" is the number in the distribution that there is the most of.
Illustration. There are twenty-one kids in a class, they take a test, and
here are the results (the "distribution"):
Students Grade Cumulative grade points
1 100 percent 100
1 95 95
3 90 270
4 85 340
6 82 492
3 80 240
2 70 140
1 65 65
21 1,742
The "mean" is computed by dividing the cum grade points by the number of
students, i.e. 1,742 divided by 21, or 82.95 per cent.
The "median" is the mid-point among the distribution - half the students
got higher, half got lower - in this case 82 is the median.
The "mode" number is that which there is the most of - here 6 students who
achieved the score of 82.
If the "median age" for diagnosis with PD is 57, then half of us were
diagnosed at an age less than 57, half at an age greater than 57.
Bob
