Vocabulary terms I need the definition

1. What is the difference between a categorical variable and a quantitative variable? 2. What is an Explanatory variable? 3. What is a Response variable? 4. How is a sample different than a population? 5. What is sampling bias? 6. What kind of sampling avoids bias? 7. What is another way of describing a confounding factor? 8. What is the difference between an observational study and an experimental study? 9. What is the placebo effect? 10. What is a matched pairs experiment