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 CR010003: In an experiment involving balls and ramps, if both the height of the ramp and the size of the ball are changed at the same time, no conclusion can be reached about the effect of either of the individual variables on how far the ball can roll.
Students have a small steel ball and a large steel ball, and they have a short ramp and a tall ramp.
The students want to find out if a ball's size affects how far it can roll. They also want to find out if the height of the ramp affects how far the ball can roll.
They do the following experiment:
What can they conclude from this experiment?
- They can conclude that the size of the balls affects how far the balls roll.
- They can conclude that the height of the ramps affects how far the balls roll.
- They can conclude that the size of the balls affects how far the balls roll and that the height of the ramps affects how far the balls roll.
- It is not possible to conclude from this experiment if the size of the balls affects how far the balls roll or if the height of the ramps affects how far the balls roll.
- Distribution of Responses
- Students Responding Correctly
| Group | Correct | Total | Percent |
|---|---|---|---|
| Overall | 856 | 2506 | 34% |
| Grades | |||
| 6–8 | 352 | 1419 | 25% |
| 9–12 | 500 | 1078 | 46% |
| Gender | |||
| Male | 441 | 1232 | 36% |
| Female | 400 | 1235 | 32% |
| Primary Language | |||
| English | 755 | 2149 | 35% |
| Other | 71 | 292 | 24% |