A researcher considers two methods for collecting data to determine if store-brand laundry detergents work as well as name-brand detergents. Method 1: The researcher surveys shoppers as they enter a grocery store. The shoppers are asked which type of detergent they use and then rate the cleanliness of their laundry on a scale from 1 to 10 (with 10 being the cleanest). The ratings of the name-brand detergents are compared to the ratings of the store-brand detergent.

Method 2: The researcher creates 10 loads of soiled fabrics and washes 5 of the loads with name-brand detergent and the other 5 with store-brand detergent. Volunteers are asked to assess the cleanliness of the fabrics using a scale from 1 to 10 (with 10 being the cleanest), and the ratings of the name-brand detergents are compared to the ratings of the store-brand detergent.

Which method describes an observational study?

Method 2 is an observational study because volunteers assess the fabrics.

Method 1 is an observational study because many people can be surveyed.

Method 1 is an observational study because no attempt is made to influence results.

Both methods are observational studies because information on both types of detergent can be collected.