Watson Kathy, Baranowski Tom, Thompson Debbe
USDA/ARS, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, 1100 Bates Street, Houston, TX 77030, USA.
Health Educ Res. 2006 Dec;21 Suppl 1:i47-57. doi: 10.1093/her/cyl136. Epub 2006 Oct 31.
Perceived self-efficacy (SE) for eating fruit and vegetables (FV) is a key variable mediating FV change in interventions. This study applies item response modeling (IRM) to a fruit, juice and vegetable self-efficacy questionnaire (FVSEQ) previously validated with classical test theory (CTT) procedures. The 24-item (five-point Likert scale) FVSEQ was administered to 1578 fourth graders from 26 Houston schools. The IRM partial credit model indicated the five-point response options were not fully utilized. The questionnaire exhibited acceptable (>0.70) reliability except at the extremes of the SE scale. Differential item functioning (DIF) analyses revealed no response bias due to gender. However, DIF was detected by ethnic groups in 10 items. IRM of this scale expanded what was known from CTT methods in three ways: (i) areas of the scale were identified that were not as reliable, (ii) limitations were found in the response format and (c) areas of the SE scale levels were not measured. The FVSEQ can be improved by including items at the extreme levels of difficulty. DIF analyses identified areas where IRM can be useful to improve the functioning of measures.
对食用水果和蔬菜的自我效能感（SE）是干预措施中调节水果和蔬菜摄入量变化的关键变量。本研究将项目反应模型（IRM）应用于先前已通过经典测试理论（CTT）程序验证的水果、果汁和蔬菜自我效能量表（FVSEQ）。对来自休斯顿26所学校的1578名四年级学生施测了包含24个项目（五点李克特量表）的FVSEQ。IRM部分计分模型表明五点反应选项未得到充分利用。除了在SE量表的极端情况外，该问卷表现出可接受的（>0.70）信度。项目功能差异（DIF）分析显示不存在因性别导致的反应偏差。然而，在10个项目中发现了不同种族群体的DIF。该量表的IRM在三个方面扩展了CTT方法所了解的内容：（i）确定了量表中可靠性较低的区域，（ii）发现了反应格式的局限性，以及（iii）未测量SE量表水平的区域。通过纳入极端难度水平的项目，可以改进FVSEQ。DIF分析确定了IRM可用于改善测量功能的领域。
