Final answer:
The data gathering technique used in this situation is an Experiment. The store owner conducts an experiment by selling only backpacks for one month and then only shoulder bags for another month to determine if shoppers prefer backpacks or shoulder bags.
Step-by-step explanation:
The data gathering technique used in this situation is an Experiment. The store owner conducts an experiment by selling only backpacks for one month and then only shoulder bags for another month to determine if shoppers prefer backpacks or shoulder bags. By manipulating the independent variable (the type of bags sold) and observing the dependent variable (shoppers' preferences), the store owner can determine which type of bag is more popular among customers.