【单选题】【消耗次数：1】
流行病学实验研究与观察性研究之间的主要区别是
①
研究是前瞻性的
②
根据患病与否选择研究组和对照组
③
研究组与对照组样本大小相同
④
调查者是否向研究对象施加干预
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相关题目
【简答题】
试述流行病学实验研究与队列研究的异同。
【单选题】
下列哪项是流行病学实验研究的优点
①
可计算相对危险度和归因危险度
②
能够及早治疗病人或预防和控制疾病
③
可平衡和控制两组的混杂因素提高两组可比性
④
省时、省钱、省力，可进行罕见病的研究
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being combined
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