1. Effect Size
EDL 204

2. Start with Hypothesis Testing
You go through the 6 steps of Hypothesis Testing and get a significant result
So what?
The probability of obtaining a significant result is highly correlated with the size of the sample
More numbers = increase probability of significance
Sometimes the impact is meaningless

3. Significance
Statistical Significance
Reached a result that has a probability of less than 5% that it is due to error
Practical Significance
Looks at whether the difference is useful in the real world
http://www.youtube.com/watch?v=rOyK_K0SOaU

4. Effect Size
d = Cohens Effect Size
1 = Mean of Group 1
2 = Mean of Group 2
= Standard Deviation

5. Effect Size
Results in a measure of standard deviation
Can be interpreted as noted by Cohen on the left
A large effect size would mean there would be a large impact on the population

6. Effect Size
Used to compare studies
Can have different
Methods
Statistics
Metrics
Only measuring the difference in mean 1 and mean 2 divided by SD

7. Visible Learning
Meta Analysis of 800 Meta Analyses
Summary of many articles on the topic
Uses Effect Sizes
1 effect size = 1 standard deviation
1 standard deviation = 2 years increase
Cohen said Blatantly obvious
PhD Students vs High School Students on IQ

8. Visible Learning
Distribution of Effect Sizes, Chapter 2, pg 16
Most have a positive effect
Doing almost anything increases achievement
Set the bar at d = 0.40
Average of all effect sizes
This is not just placing a teacher in front of a room
Benchmark to notice real differences

9. Visible Learning
Typical Effect Size
.40
0
Enhanced
Zero
Decreased

10. Visible Learning
We want...
.40
0
Enhanced
Zero
Decreased

11. Visible Learning
.40
.30
.50
.10
.20
.60
Typical
Teacher
Effects
.70
Zone of Desired Effects
Developmental Effects
.80
0
.90
Reverse Effects
1.0

12. Visible Learning
.40
.30
.50
.10
.20
.60
Typical
Teacher
Effects
.70
Zone of Desired Effects
Developmental Effects
.80
0
.90
Reverse Effects
1.0
Microteaching d = .88
pg 112-113