Department of Anatomical, Histological, Forensic & Orthopedic Sciences, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy.
BrainSigns srl, Via Lungotevere Michelangelo, 9, 00192 Rome, Italy.
Sensors (Basel). 2021 Sep 10;21(18):6088. doi: 10.3390/s21186088.
The sample size is a crucial concern in scientific research and even more in behavioural neurosciences, where besides the best practice it is not always possible to reach large experimental samples. In this study we investigated how the outcomes of research change in response to sample size reduction. Three indices computed during a task involving the observations of four videos were considered in the analysis, two related to the brain electroencephalographic (EEG) activity and one to autonomic physiological measures, i.e., heart rate and skin conductance. The modifications of these indices were investigated considering five subgroups of sample size (32, 28, 24, 20, 16), each subgroup consisting of 630 different combinations made by bootstrapping n (n = sample size) out of 36 subjects, with respect to the total population (i.e., 36 subjects). The correlation analysis, the mean squared error (MSE), and the standard deviation (STD) of the indexes were studied at the participant reduction and three factors of influence were considered in the analysis: the type of index, the task, and its duration (time length). The findings showed a significant decrease of the correlation associated to the participant reduction as well as a significant increase of MSE and STD ( < 0.05). A threshold of subjects for which the outcomes remained significant and comparable was pointed out. The effects were to some extents sensitive to all the investigated variables, but the main effect was due to the task length. Therefore, the minimum threshold of subjects for which the outcomes were comparable increased at the reduction of the spot duration.
样本量是科学研究中的一个关键问题，在行为神经科学中更是如此，因为在这些领域，除了最佳实践外，并不总是能够获得大量的实验样本。在这项研究中，我们研究了研究结果在样本量减少时如何发生变化。在涉及观察四个视频的任务中，考虑了三个计算指标，其中两个与大脑脑电图（EEG）活动有关，一个与自主生理测量有关，即心率和皮肤电导。在分析中，考虑了样本量的五个亚组（32、28、24、20、16），每个亚组由 36 个受试者中的 n（n=样本量）通过引导抽样组成 630 个不同的组合，相对于总人群（即 36 个受试者）。研究了相关性分析、均方误差（MSE）和指标的标准差（STD），在参与者减少的情况下进行了研究，并考虑了三个影响因素：指标的类型、任务及其持续时间（时间长度）。研究结果表明，随着参与者减少，相关性显著降低，MSE 和 STD 显著增加（<0.05）。指出了一个结果仍然显著和可比的参与者的阈值。这些效应在一定程度上对所有研究的变量都敏感，但主要效应是由于任务长度。因此，随着点持续时间的减少，结果可比的参与者的最小阈值增加。
