1. Andria is conducting an experiment to determine whether a new medication is effective in reducing swelling. She gets 1,000 volunteers with swelling and divides them into 2 groups. The control group does not receive any medication; the treatment group receives the medication. The patients in the treatment group show reduced signs of swelling. What can Andria conclude from this experiment?

2. Xavier is testing different types of planting soil to determine which type is most effective in growing blueberry bushes. He purchases two different brands of planting soil from a local store. Xavier applies Brand A to an area of the yard that receives full sunlight and Brand B to another area of the yard that is in partial sunlight. He waters the area with Brand B daily; he waters the area with Brand A every other day. At the end of the study, Xavier concludes Brand A is more effective in growing blueberry bushes. Why is his conclusionnotvalid?