A consumer agency wants to determine which of two laundry detergents, A or B, cleans better. Fifty 1-square-foot sections of fabric are randomly selected and cut from different bolts of fabric. They are then subjected to the same kinds of stains (grass, mud, coffee). Then 25 pieces are randomly assigned to be cleaned with detergent A, and the remaining 25 pieces are cleaned with detergent B. After being laundered, the pieces of fabric are rated on a scale of 1–10, with 1 being the least clean to 10 being the most clean. The mean rating for detergent A is found to be significantly greater than the mean rating for detergent B.

Which of the following is a valid conclusion?

Inferences can be made about the population of fabric from which the pieces were cut. The conclusion can be made that detergent A cleans better than detergent B for the fabric from these bolts.

Inferences cannot be made about the population of fabric from which the pieces were cut. The conclusion can be made that detergent A cleans better than detergent B for the fabric from these bolts.

Inferences can be made about the population of fabric from which the pieces were cut. The conclusion cannot be made that detergent A cleans better than detergent B for the fabric from these bolts.

Inferences cannot be made about the population of fabric from which the pieces were chosen. The conclusion cannot be made that detergent A cleans better than detergent B for the fabric from these bolts.