what does a scientist test when using a controlled experiment
1. a conclusion
2. serveral variables
3. a single variable
4. a mass of information
3. a single variable
When using a controlled experiment, a scientist typically tests a single variable.
When conducting a controlled experiment, a scientist typically tests a single variable. This is because the purpose of a controlled experiment is to isolate and manipulate one specific factor, while keeping all other variables constant or controlled. By doing so, the scientist can observe and measure the effect of that particular variable on the outcome of the experiment.
The use of multiple variables in an experiment would make it difficult to determine which variable is responsible for any observed changes or results. Therefore, scientists typically manipulate only one variable at a time in order to establish a cause-and-effect relationship.
So, the correct answer is: 3. a single variable.