# Should Ursula have included a control group in her experiment?

## Ursula was curious about how radioactivity affects the crystalline structure of certain minerals, so Ursula set up an experiment using the mineral zircon. First, she exposed samples of the mineral to different amounts of radiation. Then, she examined the samples using special instruments that can detect the crystalline structure of the samples.

$\text{she exposed samples of the mineral to different amounts}$ $\text{of radiation}$