Experiment Design Analysis - Gas Mileage

Marcia heard that premium unleaded gasoline gives her better gas mileage than regular unleaded. In her experiment, she filled up with tank # 1 right before she drove to Seattle. With tanks 2, 3 and 4 Marcia drove to school and work in Oak Harbor.

• 1^st tank : premium yields 22 mpg
• 2^nd tank : premium yields 20 mpg
• 3^rd tank : regular yields 20 mpg
• 4^th tank : regular yields 19 mpg

1. Question/Problem:
    
    
    
2. Hypothesis with a prediction:
    
    
    
3. Manipulated variable:
    
    
4. Levels of treatments:
    
    
5. Responding variable:
    
    
6. Controlled variable:
    
    
7. How would you improve this experiment?
    
    
    
    
8. Why did Marcia uses two tanks for each gasoline type?