Original Project
Control of Variables
If more than one variable changes at the same time in an experiment, the outcome of the experiment may not be cl…
Item CR015005: To find out which car gets better gas mileage, it is important that both cars get the same grade of gas because if they didn't, it wouldn't be possible to tell which car gets the better gas mileage.
A consumer group wants to find out which of two new car models gets the best gas mileage. A car’s gas mileage is the number of miles a car can go for each gallon of gas it uses.
They decide to fill the gas tanks of each car with the same amount of gas and compare how far each car goes. They use “regular” grade gas in both cars. Neither car gets the “premium” grade gas.
Why is it important that the two cars get the same grade of gas?
- By using the same grade of gas, the consumer group can learn both which car model gets the best mileage and which grade of gas gives the best mileage.
- By using the same grade of gas, the consumer group can learn which grade of gas gives the best mileage.
- If the cars do not get the same grade of gas, the consumer group cannot find out which car model has the best mileage.
- It is NOT important for both cars to have the same grade of gas because they are not testing which grade of gas gives the best mileage.
- Distribution of Responses
- Students Responding Correctly
| Group | Correct | Total | Percent |
|---|---|---|---|
| Overall | 2566 | 4295 | 60% |
| Grades | |||
| 6–8 | 1076 | 2038 | 53% |
| 9–12 | 1473 | 2235 | 66% |
| Gender | |||
| Male | 1231 | 2096 | 59% |
| Female | 1299 | 2139 | 61% |
| Primary Language | |||
| English | 2288 | 3739 | 61% |
| Other | 209 | 453 | 46% |