Applying circular statistics can cause artefacts in the calculation of vector coding variability: A bivariate solution
Applying circular statistics can cause artefacts in the calculation of vector coding variability: A bivariate solution
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DOI：
10.1016/j.gaitpost.2018.06.169
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发表时间：
2018-09-01
期刊：
影响因子：
2.4
通讯作者：
Preatoni, Ezio
中科院分区：
文献类型：
--
作者：
Stock, Holly;van Emmerik, Richard;Preatoni, Ezio
背景：协调变异性被认为可以为运动学习、技能水平和伤害预防提供有意义的见解。当前的分析技术基于矢量编码 (VC) 方法，使用循环统计的计算。然而，与循环统计应用相关的统计伪影可能会人为地增加估计的协调变异性，特别是当 VC 向量很短时。研究问题：计算矢量编码协调变异性的两种流行方法是否容易受到统计伪影的污染？如果是，如何在没有统计伪影的情况下计算协调变异性？方法：使用模拟和实验数据的组合来证明统计伪影的存在，并分别了解其可能影响实验跑步步态数据的程度。提出了一种使用椭圆面积作为变异性双变量度量的替代方法，应用于相同的数据集，并与两种流行的协调变异性分析方法进行比较。结果：模拟数据显示存在统计伪影，在使用圆形统计的协调变异性度量中，对于较短的 VC 向量长度，该伪影更大。统计伪影通常表现为协调变异性迹线中夸大的峰值。实验数据还表明，短矢量长度在跑步步态中普遍存在。协调变异性的椭圆面积法不受 VC 向量长度的影响。意义：使用当前 VC 变异性测量的研究人员应特别注意统计假象对其数据可能产生的影响，当向量长度较短时，这种情况最有可能发生。我们建议的计算 VC 协调变异性的新方法可能为未来矢量编码协调变异性的研究提供基础。
Background: Coordination variability is thought to provide meaningful insights into motor learning, skill level and injury prevention. Current analytical techniques, based on vector coding (VC) methods, use calculations from circular statistics. However a statistical artefact associated with the application of circular statistics may artificially increase the estimated coordination variability, especially when VC vectors are short.Research question: Are two popular methods for calculating vector coding coordination variability susceptible to contamination by statistical artefacts and if so, how can coordination variability be calculated without statistical artefact?Methods: A combination of simulated and experimental data was used to prove the existence of the statistical artefact and to understand the extent to which it may affect experimental running gait data, respectively. An alternative approach that uses ellipse area as a bivariate measure of variability was proposed, applied to the same dataset, and compared to two popular methods of coordination variability analysis.Results: The simulated data showed the existence of a statistical artefact, which was greater for shorter VC vector lengths in coordination variability measures that used circular statistics. The statistical artefact typically manifests itself as inflated peaks in the coordination variability trace. The experimental data also indicated that short vector lengths are prevalent in running gait. The Ellipse Area Method of coordination variability was not affected by the VC vector length.Significance: Researchers using current VC variability measures should be particularly aware of the possible effect of the statistical artefact on their data, which is most likely to occur when vector lengths are short. The novel approach we have suggested for calculating VC coordination variability may provide the foundation for future research into vector coding coordination variability.