LEARNING TARGET 23 EXPERIMENTAL DESIGN Researchers randomly assigned 408 adults with persistent asthma t take one of two treatments: an inhaled medicine with Vitamin D supplement or the inhaled medicine with a placebo. After seven months, the vitamin D users were no less likely to experience reduce airflow, hospitalization, or the need for additional medicine. 3. Name one variable the researchers kept the same for both group and explain why it was important to keep this variable the same