Question

which of the following best describes what makes an experiment valid?
letting each person perform the experiment in their own way
changing multiple variables at once to see all effects
only changing the independent variable while keeping everything else the same
measuring something unrelated to the experiment

Explanation:

To determine what makes an experiment valid, we analyze each option:

• "Letting each person perform the experiment in their own way" introduces variability and inconsistency, so it's invalid.
• "Changing multiple variables at once to see all effects" makes it hard to determine which variable caused a change, so it's invalid.
• "Only changing the independent variable while keeping everything else the same" is the core of a controlled experiment, allowing a clear cause - effect relationship to be established, which is what makes an experiment valid.
• "Measuring something unrelated to the experiment" doesn't help in determining the outcome of the experiment, so it's invalid.

Answer:

Only changing the independent variable while keeping everything else the same