intercept bias
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2011 ◽  
Vol 37 (3) ◽  
pp. 159-170 ◽  
Author(s):  
Robert D. Richardson ◽  
Leanne S. Hawken ◽  
John Kircher

Universal screening using curriculum-based measures allows educators to detect students who may be in need of instructional interventions. Curriculum-based measures, such as oral reading fluency and Maze, are effective at accurately and efficiently identifying reading proficiency levels for overall school populations. Nevertheless, little is currently known about whether these measures are equally predictive for the diverse populations of students in schools. The current study examined whether Maze has prediction bias for Hispanic students and for students who primarily speak Spanish at home. Slope and intercept bias were examined using hierarchical linear modeling techniques. Intercept bias was found; however, effects were small. Maze underpredicted scores on a high-stakes state language arts test for both Spanish-speaking and Hispanic students, compared to their English-speaking and Caucasian counterparts. Maze was a strong predictor of the state outcome measure and should not be ruled out as a potential universal screening measure. Implications are discussed along with suggestions for future research.


2003 ◽  
Vol 86 (4) ◽  
pp. 694-702
Author(s):  
Joe Rashan ◽  
Raymond Chen ◽  
Todd Zelesky ◽  
Sonja Sekulic

Abstract An alternative liquid chromatographic (LC) method was developed and validated for the simultaneous determination of methoxyl and 2-hydroxypropoxyl substituents in hypromellose and hypromellose acetate succinate. The method uses the hydriodic acid cleavage reaction, catalyzed by adipic acid, of the substituted methoxyl and 2-hydroxypropoxyl groups, which are quantitatively converted to iodomethane and 2-iodopropane. The iodomethane and 2-iodopropane are extracted into xylene, the extract is diluted with methanol, and the analytes are separated and assayed by gradient elution using a reversed-phase C18 column. The method is selective and sensitive and has good linearity with values of 0.999 for R2 and 0.25% for the y-intercept bias from 1.39 to 5.55 mg/mL for iodomethane, and 0.999 for R2 and 0.52% for the y-intercept bias from 0.184 to 0.735 mg/mL for 2-iodopropane. The relative standard precisions for this LC method were found to be ± 2.3% for determining methoxyl at the 23.1% (w/w) level, and ± 3.5% for determining 2-hydroxypropoxyl at the 6.7% (w/w) level. Compared with the current gas chromatographic (GC) compendial (JPE) method, the LC assay method has equal or better precision. It was found that both the standard and sample solutions have limited stability (8 h) after preparation. This limited stability has not been reported previously in the literature and may have an impact on the reported accuracy/precision of the literature data for the GC method. The LC method was proven to be robust with respect to variation in derivatization time and temperature, flow rate, and column temperature. It is well suited for the quality control needed in today's fast-paced pharmaceutical laboratories.


1992 ◽  
Vol 15 (3) ◽  
pp. 175-186 ◽  
Author(s):  
Arturo Olivárez ◽  
Douglas J. Palmer ◽  
Luisa Guillemard

Predictive bias was examined using data obtained from ethnically diverse referred and nonreferred samples. Achievement and intelligence measures included the Wechsler Intelligence Scale-Revised, Kaufman Achievement Battery, Woodcock-Johnson Psychoeducational Battery and the Woodcock Language Proficiency Battery. The sample consisted of 236 subjects selected from a large urban district in Texas. Results revealed evidence of predictive bias in several sets of intelligence-achievement measures. For the most part, intercept bias was more evident than slope bias (differential validity). The need for test developers to assess predictive bias in new or revised tests is emphasized.


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