1. Questionnaire Reliability
Personality Lab
October 5, 2010

2. Timeline for Questionnaire Assignment
Oct 5 – Discuss Questionnaire Issues
Oct 8 – Conduct Reliability Analyses
Remove unreliable items
Revise Google Docs Form i.e., subset of items from your questionnaire + items from “validity” questionnaire
Send to friends & family by end of class
Oct 11 – Start Final Analyses
Oct 12 – Discuss Analysis Issues in Class
Oct 15 – Turn in Assignment

3. Correlation Review Correlation Coefficient -1.00  0  +1.00
-1.00  0  +1.00
Coefficient indicates “strength of relationship” between two variables
-.75 equally strong as +.75
Knowing score on one variable, what can be predicted of the other variable?

4. Correlation – Neuroticism and Extraversion

5. Correlation – Optimism & Self-Esteem

6. Correlation

7. Types of Reliability Test – Retest Internal Consistency
How did your scores compare across two occasions?
Internal Consistency
Do all questionnaire items measure the same thing?

8. Satisfaction with Life
1 - Strongly disagree 4 – Neutral 7-Strongly Agree
_____1. In most ways my life is close to my ideal.
_____2. The conditions of my life are excellent.
_____3. I am satisfied with my life.
_____4. So far I have gotten the important things I want in life.
_____5. If I could live my life over, I would change almost nothing.
_____6. I love SPAM.

9. Types of Reliability, cont.
Internal Consistency
Item-total correlations
Satisfaction with Life Questions
# 1 #2 #3 #4 #5 #6
Dana 7 1
Donna 5 6
Dan 4 3
Don 2

10. Types of Reliability, cont.
Internal Consistency
Item-total correlations
Satisfaction with Life Questions with SPAM
# 1 #2 #3 #4 #5 #6
Total
Item
Dana 7 1 35
Donna 5 6 27
Dan 4 3 19
Don 2 11

11. Types of Reliability, cont.
Internal Consistency
Item-total correlations
Satisfaction with Life Questions -- Replace SPAM Item
# 1 #2 #3 #4 #5 #6
Total
Item
Dana 7 6 35
Donna 5 27
Dan 4 3 19
Don 2 11

12. Internal Consistency Split-Half Reliability Spearman-Brown Formula
R=2r/1 + r
Split-Half Reliability Using Spearman-Brown Formula
# 1 #2 #3 #4 #5 #6
1st Half
2nd Half
Dana 3 5 7 6 15 17
Donna 4 11 14
Dan 2 10 8
Don 1

13. Internal Consistency Split-Half Reliability Spearman-Brown Formula
R=2r/1 + r
Split-Half Reliability Using Spearman-Brown Formula #1 #2 #3 #4 #5 #6
1st Half
2nd Half
Dana 3 5 7 6 15 17
Donna 4 11 14
Dan 2 10 8
Don 1
Correlation Between 1st Half and 2nd Half r=.60

14. Internal Consistency Split-Half Reliability Spearman-Brown Formula
R=2r/1 + r
Split-Half Reliability Using Spearman-Brown Formula
# 1 #2 #3 #4 #5 #6
1st Half
2nd Half
Dana 3 5 7 6 15 17
Donna 4 11 14
Dan 2 10 8
Don 1
Correlation Between 1st Half and 2nd Half r=.60
R=2(.60) / = 1.2/1.6 = .75

15. Internal Consistency Cronbach’s Alpha
Average of All Split-Half Reliabilities
Split-Half Reliability Using Spearman-Brown Formula
# 1 #2 #3 #4 #5 #6
1st Half
2nd Half
Dana 3 5 7 6 14 18
Donna 4 11
Dan 2 9
Don 1
Correlation Between 1st Half and 2nd Half r=.65
R=2(.65) / = 1.3/1.65 = .79