1. Data Analysis II

2. Summarizing one variable
Mean, median, or mode
Standard error or min/max or interquartile range
Shape of distribution

3. Other issues
Floor, ceiling effect
Bimodal
ALWAYS PLOT!

4. Describing Relationships
Independent Variable
Dependent Variable
Discrete
Continuous
Cross-tab
Logit if necessary
ANOVA
Paired
t-test
Regression
Correlation

5. Cross-tabs Compare predicted frequency in a category to observed.
Example:
Expect men and women to belong at same rate
Now observe
Men
Women
Belong to env group 30 36
Don’t belong 70 64

6. Calculate Chi-squared statistic for test of H0: pi=p*

7. Cross-tabs Men Women Belong to env group 30 33 36 66 0.33 Don’t belong
Calculate relative frequency (.33, .67, .5)
Calculate expected frequencies (33, 67)
Calculate deviations (x-e) and chi-sq
Degrees of freedom=(c-1)(r-1) or 1 here
No significant difference here
Men
Women
Belong to env group 30 33 36 66
0.33
Don’t belong 70 67 64
134
0.67
100 .5

8. Describing Relationships
Independent Variable
Dependent Variable
Discrete
Continuous
Cross-tab
Logit if you have to
ANOVA
Paired
t-test
Regression
Correlation

9. Regression
Cont. DV, Discrete IV: Regress DV on IV with no intercept. Can read off F-test
Discrete DV, Cont. IV: Logit, read off p-value
Both continuous: Regression and read off p-value

10. Factor analysis for the NEP
To determine how many dimensions the 16 questions are tapping