Suzanne purchased a sweater for $25 after applying a coupon on tax free weekend. The original cost of the sweater was $40. What is the percentage discount she received by using the coupon?

b. experiment

Step-by-step explanation:

An observational study is one in which the researchers monitor the effect of a risk factor on subjects without introducing interventions for the purpose of noting differences in results. An experiment is mainly a randomized control trial where subjects are assigned to groups and chosen by chance. Interventions are also introduced by the researchers so as to note the different possible results within the groups and among participants.

The above-described process incorporates an experiment and that is why the researchers introduce protein level diet as interventions. It also employs the random assignment of subjects to different groups so as to improve the accuracy of the process.