Question

Jenny wants to determine if a new brand name washing machine is better than here old detergent. she washes ten dirty t-shirts with the new washing detergent. after washing, she thinks they are cleaner using the new detergent. what can she do to be sure the new washing detergent works better than the old detergent?
the hint is "Consider what Jenny is comparing the group treatment against."

Answer 1

I believe the answer is quite simple.

She must've compared the clothing washed with the new detergent with the old one. Jenny must've looked for stains, odour, etc. These would help determine whether or not the new detergent worked better.