### Abstract

Purpose: To test hypotheses that low vision patient responses to visual function rating scale questionnaires conform to an additive conjoint structure and that the Likert score is a sufficient statistic for the latent patient trait; to compare results for two competing stochastic measurement models; and to determine if different questionnaires measure the same construct in low vision patients. Methods: Visual function rating scale questionnaires were administered to 284 low vision subjects by telephone. Each subject was administered two of four questionnaires: ADVS, NEI VFQ-25 plus supplement, expanded VAQ, and VF-14. Results: Data were analyzed with the Muraki item response model and the Andrich measurement model. The estimates of latent person, item, and response threshold measures from the two models are linearly related. The Muraki model produced a better overall fit to the item response data, the Andrich model produced a better fit to the average ratings for each person and item. Fit statistics for the Andrich model were proportional to the item-dependent discrimination parameter in the Muraki model. The ADVS was the most accurate measure and the NEI VFQ was the least. Reliability was similar for all four instruments. Person measures for each pair of instruments were linearly related indicating that all four instruments measured the same construct. The person measure estimate from the Andrich model is monotonic with the average rating. That relationship suggests a transformation of the Likert score that can correct the floor and ceiling effects in rating scale data. Conclusions: Patient responses to all four questionnaires conform to varying degrees to an additive conjoint structure. The Likert score is a sufficient statistic for the ADVS and the VAQ, but not for the NEI VFQ_or VF-14. All four instruments measure the same construct in the low vision population, but they differ in measurement accuracy and precision.

Original language | English (US) |
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Pages (from-to) | 103-124 |

Number of pages | 22 |

Journal | Ophthalmic Epidemiology |

Volume | 12 |

Issue number | 2 |

DOIs | |

State | Published - Apr 2005 |

### Fingerprint

### Keywords

- ADVS
- Item response theory
- NEI VFQ
- Rasch analysis
- Stochastic measurement models
- VAQ
- VF-14
- Visual function rating scales

### ASJC Scopus subject areas

- Ophthalmology
- Epidemiology

### Cite this

**Application of stochastic measurement models to visual function rating scale questionnaires.** / Massof, Robert W.

Research output: Contribution to journal › Article

*Ophthalmic Epidemiology*, vol. 12, no. 2, pp. 103-124. https://doi.org/10.1080/09286580590932789

}

TY - JOUR

T1 - Application of stochastic measurement models to visual function rating scale questionnaires

AU - Massof, Robert W

PY - 2005/4

Y1 - 2005/4

N2 - Purpose: To test hypotheses that low vision patient responses to visual function rating scale questionnaires conform to an additive conjoint structure and that the Likert score is a sufficient statistic for the latent patient trait; to compare results for two competing stochastic measurement models; and to determine if different questionnaires measure the same construct in low vision patients. Methods: Visual function rating scale questionnaires were administered to 284 low vision subjects by telephone. Each subject was administered two of four questionnaires: ADVS, NEI VFQ-25 plus supplement, expanded VAQ, and VF-14. Results: Data were analyzed with the Muraki item response model and the Andrich measurement model. The estimates of latent person, item, and response threshold measures from the two models are linearly related. The Muraki model produced a better overall fit to the item response data, the Andrich model produced a better fit to the average ratings for each person and item. Fit statistics for the Andrich model were proportional to the item-dependent discrimination parameter in the Muraki model. The ADVS was the most accurate measure and the NEI VFQ was the least. Reliability was similar for all four instruments. Person measures for each pair of instruments were linearly related indicating that all four instruments measured the same construct. The person measure estimate from the Andrich model is monotonic with the average rating. That relationship suggests a transformation of the Likert score that can correct the floor and ceiling effects in rating scale data. Conclusions: Patient responses to all four questionnaires conform to varying degrees to an additive conjoint structure. The Likert score is a sufficient statistic for the ADVS and the VAQ, but not for the NEI VFQ_or VF-14. All four instruments measure the same construct in the low vision population, but they differ in measurement accuracy and precision.

AB - Purpose: To test hypotheses that low vision patient responses to visual function rating scale questionnaires conform to an additive conjoint structure and that the Likert score is a sufficient statistic for the latent patient trait; to compare results for two competing stochastic measurement models; and to determine if different questionnaires measure the same construct in low vision patients. Methods: Visual function rating scale questionnaires were administered to 284 low vision subjects by telephone. Each subject was administered two of four questionnaires: ADVS, NEI VFQ-25 plus supplement, expanded VAQ, and VF-14. Results: Data were analyzed with the Muraki item response model and the Andrich measurement model. The estimates of latent person, item, and response threshold measures from the two models are linearly related. The Muraki model produced a better overall fit to the item response data, the Andrich model produced a better fit to the average ratings for each person and item. Fit statistics for the Andrich model were proportional to the item-dependent discrimination parameter in the Muraki model. The ADVS was the most accurate measure and the NEI VFQ was the least. Reliability was similar for all four instruments. Person measures for each pair of instruments were linearly related indicating that all four instruments measured the same construct. The person measure estimate from the Andrich model is monotonic with the average rating. That relationship suggests a transformation of the Likert score that can correct the floor and ceiling effects in rating scale data. Conclusions: Patient responses to all four questionnaires conform to varying degrees to an additive conjoint structure. The Likert score is a sufficient statistic for the ADVS and the VAQ, but not for the NEI VFQ_or VF-14. All four instruments measure the same construct in the low vision population, but they differ in measurement accuracy and precision.

KW - ADVS

KW - Item response theory

KW - NEI VFQ

KW - Rasch analysis

KW - Stochastic measurement models

KW - VAQ

KW - VF-14

KW - Visual function rating scales

UR - http://www.scopus.com/inward/record.url?scp=23444440130&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=23444440130&partnerID=8YFLogxK

U2 - 10.1080/09286580590932789

DO - 10.1080/09286580590932789

M3 - Article

VL - 12

SP - 103

EP - 124

JO - Ophthalmic Epidemiology

JF - Ophthalmic Epidemiology

SN - 0928-6586

IS - 2

ER -