Point and Interval Estimates of Percentile Ranks for Scores on the Texas Functional Living Scale
ABSTRACT Point and interval estimates of percentile ranks are useful tools in assisting with the interpretation of neurocognitive test results. We provide percentile ranks for raw subscale scores on the Texas Functional Living Scale (TFLS; Cullum, Weiner, & Saine, 2009) using the TFLS standardization sample data (N = 800). Percentile ranks with interval estimates are also provided for the overall TFLS T score. Conversion tables are provided along with the option of obtaining the point and interval estimates using a computer program written to accompany this paper (TFLS_PRs.exe). The percentile ranks for the subscales offer an alternative to using the cumulative percentage tables in the test manual and provide a useful and quick way for neuropsychologists to assimilate information on the case's profile of scores on the TFLS subscales. The provision of interval estimates for the percentile ranks is in keeping with the contemporary emphasis on the use of confidence intervals in psychological statistics.
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ABSTRACT: The Texas Functional Living Scale (TFLS) is a new performance-based measure of functional abilities with an emphasis on instrumental activities of daily living skills that is brief and weighted toward cognitive tasks. The purpose of this study was to examine its psychometric properties and clinical utility in patients with Alzheimer disease (AD) and normal elderly individuals. Measures of daily functional capacities used in patients with dementia often rely upon informant-based behavioral ratings or lengthy assessments of instrumental activities of daily living. Few existing quantitative tools emphasize performance-based cognitively-oriented tasks designed for patients with AD, although there is a need for such measures. Twenty-two AD patients and 21 healthy controls were administered the TFLS and a measure of global cognitive status (Mini-Mental State Examination). Additionally, informant-based ratings of daily living skills (Blessed Dementia Rating Scale) and emotional and behavioral status (Consortium to Establish a Registry for Alzheimer's Disease Behavior Rating Scale for Dementia) were obtained from caregivers of the AD patients. All subjects were re-evaluated approximately 1 month later using the same instruments. The TFLS showed a strong correlation with the Mini-Mental State Examination (r = 0.92). At 1 month, test-retest reliability was high, and TFLS subscale scores were highly correlated (r > 0.90 for most) with the total score. The TFLS was moderately correlated with informant ratings of functional skills as assessed with the Blessed Dementia Rating Scale but was unrelated to emotional and behavioral symptoms as assessed with the Consortium to Establish a Registry for Alzheimer's Disease Behavior Rating Scale for Dementia. The TFLS showed evidence of good reliability, internal consistency, and convergent and discriminant validity with several popular measures of global cognitive status and behavioral functioning. It is a brief and easily administered performance-based measure of daily functional capabilities that is sensitive to level of cognitive impairment and seems applicable in patients with varying degrees of dementia.Neuropsychiatry, neuropsychology, and behavioral neurology 01/2001; 14(2):103-8.
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ABSTRACT: Normative data for neuropsychological tests are often presented in the form of percentiles. One problem when using percentile norms stems from uncertainty over the definitional formula for a percentile. (There are three co-existing definitions and these can produce substantially different results.) A second uncertainty stems from the use of a normative sample to estimate the standing of a raw score in the normative population. This uncertainty is unavoidable but its extent can be captured using methods developed in the present paper. A set of reporting standards for the presentation of percentile norms in neuropsychology is proposed. An accompanying computer program (available to download) implements these standards and generates tables of point and interval estimates of percentile ranks for new or existing normative data.The Clinical Neuropsychologist 04/2009; 23(7):1173-95. DOI:10.1080/13854040902795018 · 1.58 Impact Factor
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ABSTRACT: Bridges and Holler (2007) have provided a useful reminder that normative data are fallible. Unfortunately, however, their paper misleads neuropsychologists as to the nature and extent of the problem. We show that the uncertainty attached to the estimated z score and percentile rank of a given raw score is much larger than they report and that it varies as a function of the extremity of the raw score. Methods for quantifying the uncertainty associated with normative data are described and used to illustrate the issues involved. A computer program is provided that, on entry of a normative sample mean, standard deviation, and sample size, provides point and interval estimates of percentiles and z scores for raw scores referred to these normative data. The methods and program provide neuropsychologists with a means of evaluating the adequacy of existing norms and will be useful for those planning normative studies.Child Neuropsychology 04/2008; 14(2):99-117. DOI:10.1080/09297040801894709 · 2.18 Impact Factor