第23题: [单项选择]下列哪项可衡量人群中短时间内新发病例的频率() A. 发病率 B. 患病率 C. 罹患率 D. 感染率 E. 发病比 参考答案:C 答案解析:罹患率是测量新发病例频率的指标。它常用来衡量人群中在较短时间内新发病例的频率。观察时间可用日、周、旬、月为单位,常用于疾病流行或暴发的病因调查。
第30题: [单项选择]Which of the following statements regarding marginal costs (MC) and average variable costs (AVC) is most accurate() A. MC = AVC when AVC is at its minimum. B. MC < AVC when AVC is at its minimum. C. MC = Average total cost when AVC is at its minimum. 参考答案:A 答案解析:
MC = AVC at minimum average variable cost. MC = ATC at minimum average total cost.