This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
[{'content': "Test based on counting the direction of each within paired sample is- \nSelect and explain. \nA. .'t' test, B. Z test, C. F test, D. Sign test", 'role': 'user'}, {'content': "Answer: D \nExplanation: * The 'Sign test' is non parametric / distribution free test which can be utilized to analyze paired sample * It is based on counting the direction (or Sign) of each 'within-pair difference", 'role': 'assistant'}]