Standard Deviation
- is a measure of how much scores differ from their mean
64% around average (first deviation)
30% a bit more above average or below (2nd deviation)
5% way above average or below (3rd deviation)
1% outliers
64% around average (first deviation)
30% a bit more above average or below (2nd deviation)
5% way above average or below (3rd deviation)
1% outliers
Ex:
20 questions
Scores: 10, 11, 11, 13, 14, 19
Average: 13
Formula: Rad. Σx^2 /2 = d
Σ = sum
10-13 -3
11-13 -2
11-13 -2
13-13 0
14-13 1
19-13 6
Square all
9, 4, 4, 0, 1, 36
Add up. Sum = 54
rad. 54/6 = 3
Anyone who score in between 10 - 16 is 1st deviation
The person who score 19 is on the line between the 2nd and the 3rd deviation
Class height: 149, 175, 185, 154, 173, 156, 179/ 7
~~ 167
-18, 8, 18, 15, -13, 6, 12
Deviation =27
20 questions
Scores: 10, 11, 11, 13, 14, 19
Average: 13
Formula: Rad. Σx^2 /2 = d
Σ = sum
10-13 -3
11-13 -2
11-13 -2
13-13 0
14-13 1
19-13 6
Square all
9, 4, 4, 0, 1, 36
Add up. Sum = 54
rad. 54/6 = 3
Anyone who score in between 10 - 16 is 1st deviation
The person who score 19 is on the line between the 2nd and the 3rd deviation
Class height: 149, 175, 185, 154, 173, 156, 179/ 7
~~ 167
-18, 8, 18, 15, -13, 6, 12
Deviation =27