A detergent manufacturer (the White Soap Co.) is concerned about claims made by a rival firm (Bright Detergent, Inc.) that Bright detergent results in cleaner clothes than White detergent. Twelve dirty sheets are randomly assigned to the two detergents and washed (in identical washing machines).

After washing, the cleanliness of each shirt is measured on a “Bright-OMeter,” with the following results (a cleaner sheet will have a higher rating):