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 CR002003: An experiment in which the amount of sunlight is varied and the minerals in the plant's water is held constant could tell you the effect of light on plant growth.
A student wants to find out if a particular kind of plant grows better in the sun or in the shade. She has two identical plants. She places one plant in sand and sets the plant in the sunlight. She adds minerals and water to the sand.
| Sunlight |
|
| Water and minerals |
Which of the following conditions should she use for the second plant to determine the effect of light?
-
Sunlight 
Water and minerals -
Sunlight 
Water -
Shade 
Water and minerals -
Shade 
Water
TIMSS population 2 item pool (N-1), 1994
- Distribution of Responses
- Students Responding Correctly
| Group | Correct | Total | Percent |
|---|---|---|---|
| Overall | 1620 | 2314 | 70% |
| Grades | |||
| 6–8 | 770 | 1230 | 63% |
| 9–12 | 844 | 1076 | 78% |
| Gender | |||
| Male | 766 | 1135 | 67% |
| Female | 829 | 1142 | 73% |
| Primary Language | |||
| English | 1456 | 2032 | 72% |
| Other | 125 | 222 | 56% |