1. Reliability

2. How to test Repeat the same test with the same group
Use the same test with different group
In general Observe = True + Error
Reliability = Var(True) / Var(Error)
Data
Quantitative – Scale and Ratio
Ordinal Scale

3. Quantitative (Pearson correlation)

4. Ordinal Scale (Spearman Rank Correlation)

5. Split – Half Method (Spearman Brown)

6. Cronbachs’ Alpha Coefficient
This value is minimum of reliability of True Component.
The Cronbaschs’s alpha will increase when question increases.

7. Kuder – Richardson (For Dichotomous)
K-R20
K-R21

8. From SPSS (Example_Reliability)

9. Assignment
Test the reliability of important variables (Key variable) using the different style of correlation.
Collect more data and check reliability again.