Four detergents' cleaning action were compared. Seventeen pieces of white cloth were first soiled with India ink. After washing the cloth pieces with four different detergents, the whiteness readings...

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Extracted text: Four detergents' cleaning action were compared. Seventeen pieces of white cloth were first soiled with India ink. After washing the cloth pieces with four different detergents, the whiteness readings for the 17 pieces of cloth are shown below. Detergent A B C D 77 74 73 76 81 66 78 85 61 58 57 77 76 69 64 69 63 Assuming all whiteness readings to be normally distributed with common variance, test the hypothesis of no difference between the four brands' mean whiteness readings after washing. Note: Do all calculation round off to two decimals.]