In items 1-4 below, I need to "make up" the name for the independent or grouping variable (depending on whether the study is an experimental or casual-comparative study). In what steps do I need to include information in?

1. Is there a relationship between years of post-secondary schooling and social competence?
2. How will learners enrolled in an intensive mathematics program during the summer achieve in math compared to those who are not enrolled in the program? (Learners were not assigned randomly to condition).
3. What is the relationship among high school rank, ACT scores, time spent studying, a positive attitude toward school, and a successful collegiate experiences?
4. Are there differences between rural and urban children's attitudes regarding diversity?