Question

a consumer agency wants to determine which of two laundry detergents, a or b, cleans better. fifty pieces of fabric are 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 from 1–10, with 1 being the least clean to 10 being the most clean. the difference in mean ratings (a - b) was determined to be -2.3. assuming there is no difference in the two detergents, 200 simulated differences in sample means are displayed in the dotplot. simulation for difference in mean detergent ratings (dotplot with axis from -3.0 to 3.0)

Explanation:

Answer:

Since the observed difference in mean ratings \((A - B)=-2.3\) is in the tail of the dot - plot (assuming the dot - plot has few or no dots at \(-2.3\)), we reject the null hypothesis. There is evidence that there is a difference in the cleaning ability of the two detergents. Since \(A - B=-2.3\), detergent \(B\) cleans better.