Department of Sport and Health Sciences, Technical University of Munich, Georg-Brauchle-Ring 62, 80992, Munich, Germany.
Department of Mathematics, Technical University of Munich, Boltzmannstraße 3, 85748, Garching, Germany.
BMC Public Health. 2020 Jun 22;20(1):979. doi: 10.1186/s12889-020-09096-4.
The majority of children and adolescents are insufficiently physically active. Self-efficacy is considered one of the most important determinants of physical activity (PA). The purpose of this study was to validate the German version of the physical activity self-efficacy scale by means of a multi-level approach. Factorial validity, internal consistency and criterion validity were examined for the individual and the class level.
The final sample comprised 454 female sixth-graders of 33 classes. To examine the factorial validity of the translated 8-item scale, a multi-level confirmatory factor analysis was conducted with the lavaan package in R. Internal consistency was estimated with the alpha function of the psych package. Criterion validity was examined by correlating self-efficacy with moderate-to-vigorous physical activity (MVPA) assessed with accelerometers.
In contrast to previous validation studies, a unidimensional structure of the scale was not supported. Instead, two highly correlated (r = .87; r = .69) but distinct latent factors, representing PA self-efficacy and social support from family and friends, were differentiated on both the individual and class level. The best overall fit exhibited a multi-level 1 × 1-model, including only the six items measuring PA self-efficacy (χ2 = 32.10, CFI = .986, TLI = .976, RMSEA = .059, SRMR = .035). Internal consistencies for the complete 8-item scale and the 6-item scale were good on the individual level and excellent on the class level. For the two items measuring social support, Cronbach's alpha was low on the individual and excellent on the class level. Weak relations between self-efficacy and MVPA were found for the individual level, strong associations were found for the class level.
The validation speaks for the use of the abridged 6-item scale, which allows for a unidimensional assessment of PA self-efficacy. Generally, the results support the relevance of a multi-level approach, which not only differentiates between self-efficacy on the individual level and on the class level but also between the respective implications regarding reliability and criterion validity on both levels. Thereby, this study offers a rigorously validated scale and further illustrates possible consequences of the usual neglect of group-level variance in scale validation.
大多数儿童和青少年的身体活动量不足。自我效能感被认为是身体活动（PA）的最重要决定因素之一。本研究旨在通过多层次方法验证身体活动自我效能感量表的德语版本。在个体和班级层面上检查了因子有效性、内部一致性和效标效度。
最终样本包括 33 个班的 454 名六年级女生。为了检验翻译后的 8 项量表的因子有效性，使用 R 中的 lavaan 包进行了多层次验证性因子分析。使用 psych 包的 alpha 函数估计内部一致性。通过与加速度计评估的中等到剧烈体力活动（MVPA）相关联，检验效标效度。
与之前的验证研究不同，该量表的单维结构未得到支持。相反，在个体和班级层面上，两个高度相关（r=0.87；r=0.69）但不同的潜在因素，代表 PA 自我效能感和来自家庭和朋友的社会支持，得到了区分。具有最佳整体拟合度的是包括仅测量 PA 自我效能感的 6 个项目的多层次 1×1 模型（χ2=32.10，CFI=0.986，TLI=0.976，RMSEA=0.059，SRMR=0.035）。完整的 8 项量表和 6 项量表在个体层面上的内部一致性良好，在班级层面上的内部一致性优秀。对于测量社会支持的两项指标，个体层面的 Cronbach's alpha 较低，而班级层面的 Cronbach's alpha 较高。在个体层面上，自我效能感与 MVPA 之间的关系较弱，而在班级层面上的关系较强。
验证支持使用简化的 6 项量表，该量表允许对 PA 自我效能感进行单一维度评估。总的来说，结果支持多层次方法的相关性，该方法不仅区分了个体层面和班级层面的自我效能感，还区分了两个层面上的可靠性和效标效度的各自含义。因此，本研究提供了一个经过严格验证的量表，并进一步说明了在量表验证中通常忽略群体层面方差的可能后果。
