2.研究对象
这一部分需要对研究对象（Sample，Participants，Subjects）进行描述，包括：样本来源或研究对象招募场所、样本量、抽样方法、纳入和排除标准。有些期刊明确要求说明样本量计算方法，所以在研究设计阶段，就要对此方面进行仔细考量。
如示例2-38所示，该研究介绍了样本来源以及样本量计算方法。如示例2-39所示，该研究介绍了样本量及研究对象的招募方法和场所。
示例2-38 样本来源及样本量计算
Sample and procedure
The study took place within a large care organization in the Netherlands，counting 17 nursing homes，with about 2000 employees.Taking into account a 25%loss to follow-up，a power analysis indicated that 86 participants divided over two groups were needed to have 80%power for detecting a smallsized effect.
示例2-39 样本量、招募场所和方法
Participants
We aimed to recruit 404 participants and achieved a final sample size of 410（205 in each arm）.Participants were recruited from the community through multiple channels；for example，the study web-link was sent to contact lists of people who had previously expressed an interest in taking part in sleep research and advertised on websites and social media platforms.
多数情况下，需要对纳入标准和排除标准进行详细描述，以便供其他研究人员参考。有时候，针对某个纳入或排除标准，需要说明设置此标准的原因或相应的支撑文献（例如，某疾病诊断标准）。如示例2-40所示，研究给出了具体的纳入和排除标准，同时给出了相应的引文进行支持。(https://www.daowen.com)
示例2-40 纳入和排除标准（含引文支撑疾病诊断）
Inclusion criteria were（1）aged 25 years and older，（2）meet DSM-5 criteria for insomnia disorder according to the Sleep Condition Indicator［21］，（3）report difficulties with concentration or memory［22］，（4）have reliable Internet access，（5）read and understand English，and（6）currently reside in the United Kingdom.Exclusion criteria were（1）screen positive for or report a diagnosis of additional sleep disorder［23］，（2）report a diagnosis of mild cognitive impairment，dementia.
另外，对于二次分析，可以通过引用既往发表过的论文，而不再赘述。但是，需要对所提供的信息量进行权衡。一方面，本论文没有必要对既往介绍过的内容逐字逐句进行描述，这反而会增加论文与既往文献的重复率（一旦你的论文发表出来，它就不再属于你而属于出版商）；另一方面，论文所提供的内容不可过于简短。对于审稿人来说，论文要为他们提供足够的信息，以便其对论文进行审阅，这一点对于审稿人来说尤其重要。虽然他们可以通过查询你所引用的原始文献获取更加详细的信息，但是很少有审稿人愿意花费更多的时间获取此文献。此种情况下，可以采取以下撰写策略：Detailed inclusion and exclusion criteria have been described in a previous report.In brief...（大致介绍一下纳入和排除标准，而无须给出选择某纳入或排除标准的原因）。如示例2-41和示例2-42所示，该论文通过引用既往发表过的文献，介绍了研究对象。
示例2-41 研究对象举例1
Participants
All participants were members of the prospective occupational cohort study，Whitehall Ⅱ［13］and the Whitehall II Imaging Sub-Study［14］.
示例2-42 研究对象举例2
The DPP
The DPP was a multicenter randomized control trial with a median follow-up of 3.2 years among individuals at high risk for diabetes.Inclusion and exclusion criteria were published previously（14）.