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Measurement Validity of the Low Vision Independence Measure (LVIM)
Theresa M Smith1, Shilpa Krishnan1, Ickpyo Hong1
1Theresa M. Smith, PhD, OTR, CLVT, is Associate Professor, School of Occupational Therapy, Texas Woman's University, Houston; tsmith12@twu.edu. At the time of this research, she was Associate Professor, Department of Occupational Therapy, University of Texas Medical Branch, Galveston.
Objective:
This study's objective was to test the psychometrics of Smith's (2013) Low Vision Independence Measure (LVIM) using the Rasch model.
Method:
A cohort design was used with 93 participants receiving occupational therapy for low vision. Confirmatory factor analysis (CFA) with a parceling approach was used to test the LVIM factors and Rasch analysis to examine item-level psychometrics.
Results:
Participants' average age was 78.9 yr (standard deviation = 12.1), and the majority were female (72.8%) with macular degeneration (62.3%). The CFA revealed two measurement factors: visual field or scotoma (n = 28) and visual acuity (n = 24). We removed six misfitting items, and the two factors of the revised LVIM demonstrated good rating scale function, good internal consistency (person reliability: visual field, .87; visual acuity, .90), good precision (person strata: visual field, 3.91; visual acuity, 4.40), no ceiling or floor effects, and no differential item functioning.
Conclusion:
The revised LVIM demonstrates good psychometrics on the Rasch model and can be used as a valid outcome measure in low vision rehabilitation.
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Introduction to Test of Independence
The test statistic for a test of independence is similar to that of a goodness-of-fit test:
Hypothesis Test for Test of Independence
H0: The two variables (factors)...

