Percentage decrease in mean diarrhea duration

Steps:

• Original mean duration (oral rehydration): 5.0 days
• New mean duration (antibiotic): 3.2 days
• Difference: 5.0 - 3.2 = 1.8 days
• Percentage decrease: (1.8 / 5.0) × 100% = 36%

Why A is correct:

• Percentage decrease formula ((original - new)/original × 100%) yields 36% for the given means.

Why the others are wrong:

• B: 60% assumes difference of 3.0 days, not 1.8
• C: 65% assumes difference of 3.25 days, exceeding actual reduction
• D: 25% assumes difference of 1.25 days, understating the reduction

Final answer: A