研究对象(材料)选择的正确与否,不但影响到研究(调查)结果的可信性,还将决定所得结论能否成立。因此,正确选择研究对象(材料)是完成每项科研工作的基础。某作者在“医院乙型肝炎表面抗原污染调查”中,选择“取耳垂血用过的刮血片、口腔和妇产科术后的器械”为调查材料。作者的目的是想通过检测这些医用器械HBsAg的污染情况,来揭示医用器械作为乙型肝炎医源性传播媒介的意义。术后医用器械HBsAg的检出,的确可提示医疗器械作为乙肝传播媒介的这种可能性,但作者忽略了一点,即这些被污染的器械在再次使用前是经过严格消毒的。如果消毒是彻底的,即使用过的医用器械中可检出HBsAg,也未必造成HBsAg的传播,即这些调查材料并不能反映出具有流行病学现实意义的医院乙型肝炎表面抗原的污染情况。那么应该如何正确选择调查对象呢?选择调查对象应遵循的原则是:保证从调查对象中能获得需要的 Whether the research object (material) is chosen correctly or not will not only affect the credibility of the research (survey) results, but also determine whether the conclusions can be obtained. Therefore, the correct choice of subjects (materials) is to complete each of the basis of scientific research. One of the authors in the “hospital hepatitis B surface antigen contamination survey”, select “used ear lobe blood scraping film, oral and obstetrics and gynecology instruments” for the investigation of the material. The author’s intention is to discover the significance of medical devices as iatrogenic vectors of hepatitis B by detecting the contamination of these devices with HBsAg. The detection of postoperative medical devices HBsAg can indeed prompt the possibility of medical devices as a hepatitis B transmission medium, but the author overlooks the fact that these contaminated devices are severely sterilized before they are used again. If disinfection is complete, the detection of HBsAg in used medical devices does not necessarily lead to the spread of HBsAg, ie, these survey materials do not reflect the epidemiological significance of hospital-acquired hepatitis B surface antigen contamination. So how to choose the right respondents? The choice of respondents should follow the principle is: to ensure that from the respondents to obtain the necessary