Statistical analysis with missing data
Statistical analysis with missing data
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The National Institute for Occupational Safety and Health (NIOSH) conducted a head-and-face anthropometric survey of diverse, civilian respirator users. Of the 3,997 subjects measured using traditional anthropometric techniques, surface scans and 26 three-dimensional (3-D) landmark locations were collected for 953 subjects. The objective of this study was to analyze the size and shape variation of the survey participants using 3-D Generalized Procrustes Analysis (GPA) in order to quantify those facial features that may be relevant to respirator fit using Principal Component Analysis (PCA). The first four principal components (PC) account for 49% of the total sample variation. The first PC indicates that overall size is an important component of facial variability. The second PC accounts for long and narrow or short and wide faces. Longer narrow orbits versus shorter wider orbits can be described by PC3, and PC4 represents variation in the degree of ortho/prognathism with positively scoring individuals having longer, wider, and more projecting lower jaws than negatively scoring individuals. Further study will investigate the correlation between respirator fit and these PCs.