Maximizing Power in Generalizability Studies Under Budget Constraints

1993 ◽  
Vol 18 (2) ◽  
pp. 197-206 ◽  
Author(s):  
George A. Marcoulides
Keyword(s):  
Error Control ◽  
Resource Constraints ◽  
Generalizability Theory ◽  
Error Variance ◽  
Test Reliability ◽  
Simple Task ◽  
Mean Error ◽  
Measurement Design ◽  
The Mean ◽  
Statistical Issues

Generalizability theory provides a framework for examining the dependability of behavioral measurements. When designing generalizability studies, two important statistical issues are generally considered: power and measurement error. Control over power and error of measurement can be obtained by manipulation of sample size and/or test reliability. In generalizability theory, the mean error variance is an estimate that takes into account both these statistical issues. When limited resources are available, determining an optimal measurement design is not a simple task. This article presents a methodology for minimizing mean error variance in generalizability studies when resource constraints are imposed.

Revision of a Criterion-Referenced Vocabulary Test Using Generalizability Theory

2009 ◽  
Vol 31 (1) ◽  
pp. 81
Author(s):  
Takeaki Kumazawa
Keyword(s):  
Generalizability Theory ◽  
Classical Test Theory ◽  
Performance Testing ◽  
Error Variance ◽  
Test Theory ◽  
Vocabulary Test ◽  
Multiple Sources ◽  
Generalizability Coefficient ◽  
Criterion Referenced ◽  
Generalizability Study

Classical test theory (CTT) has been widely used to estimate the reliability of measurements. Generalizability theory (G theory), an extension of CTT, is a powerful statistical procedure, particularly useful for performance testing, because it enables estimating the percentages of persons variance and multiple sources of error variance. This study focuses on a generalizability study (G study) conducted to investigate such variance components for a paper-pencil multiple-choice vocabulary test used as a diagnostic pretest. Further, a decision study (D study) was conducted to compute the generalizability coefficient (G coefficient) for absolute decisions. The results of the G and D studies indicated that 46% of the total variance was due to the items effect; further, the G coefficient for absolute decisions was low. 古典的テスト理論は尺度の信頼性を測定するため広く用いられている。古典的テスト理論の応用である一般化可能性理論（G理論）は特にパフォーマンステストにおいて有効な分析手法であり、受験者と誤差の要因となる分散成分の割合を測定することができる。本研究では診断テストとして用いられた多岐選択式語彙テストの分散成分を測定するため一般化可能性研究（G研究）を行った。さらに、決定研究（D研究）では絶対評価に用いる一般化可能性係数を算出した。G研究とD研究の結果、項目の分散成分が全体の分散の46%を占め、また信頼度指数は高くなかった。

Measurements of the excess volume of benzene-methanol, benzene-acetonitrile and methanol-acetonitrile mixtures by a vibrating-tube densimeter

1979 ◽  
Vol 44 (2) ◽  
pp. 295-306 ◽  
Author(s):  
Ivan Cibulka ◽  
Vladimír Hynek ◽  
Robert Holub ◽  
Jiří Pick
Keyword(s):  
Excess Volume ◽  
Density Measurement ◽  
Indirect Measurement ◽  
Measuring System ◽  
Mean Error ◽  
Shaped Tube ◽  
Underlying Principle ◽  
The Mean ◽  
Vibrating Tube Densimeter

A digital vibrating-tube densimeter was constructed for measuring the density of liquids at several temperatures. The underlying principle of the apparatus is the measurement of the period of eigen-vibrations of a V-shaped tube; the second power of the period of the vibrations is proportional to the density of the liquid in the tube. The temperature of the measuring system is controlled by an electronic regulator. The mean error in the density measurement is approximately ±1 . 10-5 g cm-3 at 25 °C and ±2 . 10-5 g cm-3 at 40 °C. The apparatus was used for an indirect measurement of the excess volume, tested with the benzene-cyclohexane system and further used for determining the excess volume of the benzene-methanol, benzene-acetonitrile and methanol-acetonitrile systems at 25 and 40 °C.

scholarly journals Applying generalizability theory to examine assessments of subjective cognitive complaints: whose reports should we rely on – participant versus informant?

2021 ◽  
pp. 1-11
Author(s):  
Q. C. Truong ◽  
C. Choo ◽  
K. Numbers ◽  
A. G. Merkin ◽  
H. Brodaty ◽  
...  
Keyword(s):  
Predominantly White ◽  
Generalizability Theory ◽  
The Elderly ◽  
Community Dwelling ◽  
Assessment Tools ◽  
Sample Population ◽  
Cognitive Complaints ◽  
Longitudinal Measurement ◽  
Measurement Design ◽  
Subjective Cognitive Complaints

ABSTRACT Objectives: This study aimed to apply the generalizability theory (G-theory) to investigate dynamic and enduring patterns of subjective cognitive complaints (SCC), and reliability of two widely used SCC assessment tools. Design: G-theory was applied to assessment scales using longitudinal measurement design with five assessments spanning 10 years of follow-up. Setting: Community-dwelling older adults aged 70–90 years and their informants, living in Sydney, Australia, participated in the longitudinal Sydney Memory and Ageing Study. Participants: The sample included 232 participants aged 70 years and older, and 232 associated informants. Participants were predominantly White Europeans (97.8%). The sample of informants included 76 males (32.8%), 153 females (65.9%), and their age ranged from 27 to 86 years, with a mean age of 61.3 years (SD = 14.38). Measurements: The Memory Complaint Questionnaire (MAC-Q) and the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE). Results: The IQCODE demonstrated strong reliability in measuring enduring patterns of SCC with G = 0.86. Marginally acceptable reliability of the 6-item MAC-Q (G = 0.77–0.80) was optimized by removing one item resulting in G = 0.80–0.81. Most items of both assessments were measuring enduring SCC with exception of one dynamic MAC-Q item. The IQCODE significantly predicted global cognition scores and risk of dementia incident across all occasions, while MAC-Q scores were only significant predictors on some occasions. Conclusions: While both informants’ (IQCODE) and self-reported (MAC-Q) SCC scores were generalizable across sample population and occasions, self-reported (MAC-Q) scores may be less accurate in predicting cognitive ability and diagnosis of each individual.

scholarly journals New Methodology for Computing the Aircraft’s Position Based on the PPP Method in GPS and GLONASS Systems

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2525
Author(s):  
Kamil Krasuski ◽  
Damian Wierzbicki
Keyword(s):  
Linear Combination ◽  
Research Method ◽  
High Efficiency ◽  
Satellite System ◽  
Weighting Scheme ◽  
Measurement Technology ◽  
Dual Frequency ◽  
Weighted Mean ◽  
Mean Error ◽  
The Mean

In the field of air navigation, there is a constant pursuit for new navigation solutions for precise GNSS (Global Navigation Satellite System) positioning of aircraft. This study aims to present the results of research on the development of a new method for improving the performance of PPP (Precise Point Positioning) positioning in the GPS (Global Positioning System) and GLONASS (Globalnaja Nawigacionnaja Sputnikovaya Sistema) systems for air navigation. The research method is based on a linear combination of individual position solutions from the GPS and GLONASS systems. The paper shows a computational scheme based on the linear combination for geocentric XYZ coordinates of an aircraft. The algorithm of the new research method uses the weighted mean method to determine the resultant aircraft position. The research method was tested on GPS and GLONASS kinematic data from an airborne experiment carried out with a Seneca Piper PA34-200T aircraft at the Mielec airport. A dual-frequency dual-system GPS/GLONASS receiver was placed on-board the plane, which made it possible to record GNSS observations, which were then used to calculate the aircraft’s position in CSRS-PPP software. The calculated XYZ position coordinates from the CSRS-PPP software were then used in the weighted mean model’s developed optimization algorithm. The measurement weights are a function of the number of GPS and GLONASS satellites and the inverse of the mean error square. The obtained coordinates of aircraft from the research model were verified with the RTK-OTF solution. As a result of the research, the presented solution’s accuracy is better by 11–87% for the model with a weighting scheme as a function of the inverse of the mean error square. Moreover, using the XYZ position from the RTKLIB program, the research method’s accuracy increases from 45% to 82% for the model with a weighting scheme as a function of the inverse of the square of mean error. The developed method demonstrates high efficiency for improving the performance of GPS and GLONASS solutions for the PPP measurement technology in air navigation.

scholarly journals Assessment of necessity of neuronavigation in localization of calvarial extra-axial lesions in the setting of limited resources

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Hussein Soffar ◽  
Mohamed F. Alsawy
Keyword(s):  
Conventional Method ◽  
Linear Measurement ◽  
Limited Resources ◽  
Linear Measurements ◽  
Surgical Interventions ◽  
Localization Method ◽  
Mean Error ◽  
Significant Difference ◽  
The Mean ◽  
Mean Time

Abstract Background Neuronavigation is a very beneficial tool in modern neurosurgical practice. However, the neuronavigation is not available in most of the hospitals in our country raising the question about its importance in localizing the calvarial extra-axial lesions and to what extent it is safe to operate without it. Methods We studied twenty patients with calvarial extra-axial lesions who underwent surgical interventions. All lesions were preoperatively located with both neuronavigation and the usual linear measurements. Both methods were compared regarding the time consumed to localize the tumor and the accuracy of each method to anticipate the actual center of the tumor. Results The mean error of distance between the planned center of the tumor and the actual was 6.50 ± 1.762 mm in conventional method, whereas the error was 3.85 ± 1.309 mm in IGS method. Much more time was consumed during the neuronavigation method including booting, registration, and positioning. A statistically significant difference was found between the mean time passed in the conventional method and IGS method (2.05 ± 0.826, 24.90 ± 1.334, respectively), P-value < 0.001. Conclusion In the setting of limited resources, the linear measurement localization method seems to have an accepted accuracy in the localization of calvarial extra-axial lesions and it saves more time than neuronavigation method.

scholarly journals A queueing model for error control of partial buffer sharing in ATM

1999 ◽  
Vol 5 (4) ◽  
pp. 329-348
Author(s):  
Boo Yong Ahn ◽  
Ho Woo Lee
Keyword(s):  
Error Control ◽  
Approximation Scheme ◽  
Queueing System ◽  
Recursive Method ◽  
Loss Probabilities ◽  
Mean Waiting Time ◽  
System Equations ◽  
The Mean ◽  
Buffer Sharing

We model the error control of the partial buffer sharing of ATM by a queueing systemM1,M2/G/1/K+1with threshold and instantaneous Bernoulli feedback. We first derive the system equations and develop a recursive method to compute the loss probabilities at an arbitrary time epoch. We then build an approximation scheme to compute the mean waiting time of each class of cells. An algorithm is developed for finding the optimal threshold and queue capacity for a given quality of service.

The Influence of Training Phase on Error of Measurement in Jump Performance

2016 ◽  
Vol 11 (2) ◽  
pp. 235-239 ◽  
Author(s):  
Kristie-Lee Taylor ◽  
Will G. Hopkins ◽  
Dale W. Chapman ◽  
John B. Cronin
Keyword(s):  
Mixed Model ◽  
Training Phase ◽  
Confidence Limits ◽  
Mean Power ◽  
Random Factor ◽  
Jump Performance ◽  
Mean Error ◽  
Overload Training ◽  
The Mean ◽  
Error Of Measurement

The purpose of this study was to calculate the coefficients of variation in jump performance for individual participants in multiple trials over time to determine the extent to which there are real differences in the error of measurement between participants. The effect of training phase on measurement error was also investigated. Six subjects participated in a resistance-training intervention for 12 wk with mean power from a countermovement jump measured 6 d/wk. Using a mixed-model meta-analysis, differences between subjects, within-subject changes between training phases, and the mean error values during different phases of training were examined. Small, substantial factor differences of 1.11 were observed between subjects; however, the finding was unclear based on the width of the confidence limits. The mean error was clearly higher during overload training than baseline training, by a factor of ×/÷ 1.3 (confidence limits 1.0–1.6). The random factor representing the interaction between subjects and training phases revealed further substantial differences of ×/÷ 1.2 (1.1–1.3), indicating that on average, the error of measurement in some subjects changes more than in others when overload training is introduced. The results from this study provide the first indication that within-subject variability in performance is substantially different between training phases and, possibly, different between individuals. The implications of these findings for monitoring individuals and estimating sample size are discussed.

scholarly journals Development of the Persian version of high-frequency emphasis quick speech in noise

2019 ◽  
Author(s):  
Jamileh Fatahi ◽  
Maryam Amiri Jahromi ◽  
Fahimeh Hajiabolhassan ◽  
Amirsalar Jafarpisheh ◽  
Nariman Rahbar ◽  
...  
Keyword(s):  
High Frequency ◽  
Signal To Noise Ratio ◽  
Mean Value ◽  
Small Sample ◽  
Test Reliability ◽  
Face Validity ◽  
Mean Values ◽  
Speech In Noise ◽  
Persian Version ◽  
The Mean

Background and Aim: The quick speech in noise (Q-SIN) test shows the difficulty of spee­ch perception in noise by specifying signal to noise ratio (SNR) loss. Although the Persian version of Q-SIN has been already constructed, the high-frequency emphasis version of this test is not available. The present study aimed to construct six lists with high-frequency emphasis and implement it. Methods: We are going to prepare a high-frequ­ency emphasis version of Q-SIN and then test it on a small sample. First, researchers designed the relevant sentences; then experts examined their content and face validity. According to the criteria for developing the Q-SIN test, six lists with high-frequency emphasis were prepared. The test was examined on 26 (13 male and 13 female), 18−35 years old individuals with nor­mal hearing. To determine the test reliability, it was re-administered three weeks later with the same conditions. Results: Of 76 sentences prepared, 36 sentences received enough credit after determination of their content and face validity. These 36 senten­ces were used to make 6 lists. The mean value of SNR50 in the Persian language was obtained -4 dB. The mean values of SNR loss in 6 lists were -1.65, -1.8, -2.23, -1.61, -2.38 and -2.07. The results showed equivalency of lists 1, 2, 3, 4, and 6. Examination of test-retest reliability indicated that all lists except the list 2were reliable. Conclusion: The lists of 1, 3, 4, and 6 are reli­able and equivalent and can be used in clinical application.

scholarly journals The affectability of writing assessment scores: a G-theory analysis of rater, task, and scoring method contribution

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ali Khodi
Keyword(s):  
Writing Assessment ◽  
Generalizability Theory ◽  
Error Variance ◽  
Total Variance ◽  
Scoring Method ◽  
Writing Assessments ◽  
Assessment Scores ◽  
Peer Rating ◽  
Reliable Assessment ◽  
Writing Scores

AbstractThe present study attempted to to investigate  factors  which affect EFL writing scores through using generalizability theory (G-theory). To this purpose, one hundred and twenty students participated in one independent and one integrated writing tasks. Proceeding, their performances were scored by six raters: one self-rating,  three peers,-rating and two instructors-rating. The main purpose of the sudy was to determine the relative and absolute contributions of different facets such as student, rater, task, method of scoring, and background of education  to the validity of writing assessment scores. The results indicated three major sources of variance: (a) the student by task by method of scoring (nested in background of education) interaction (STM:B) with 31.8% contribution to the total variance, (b) the student by rater by task by method of scoring (nested in background of education) interaction (SRTM:B) with 26.5% of contribution to the total variance, and (c) the student by rater by method of scoring (nested in background of education) interaction (SRM:B) with 17.6% of the contribution. With regard to the G-coefficients in G-study (relative G-coefficient ≥ 0.86), it was also found that the result of the assessment was highly valid and reliable. The sources of error variance were detected as the student by rater (nested in background of education) (SR:B) and rater by background of education with 99.2% and 0.8% contribution to the error variance, respectively. Additionally, ten separate G-studies were conducted to investigate the contribution of different facets across rater, task, and methods of scoring as differentiation facet. These studies suggested that peer rating, analytical scoring method, and integrated writing tasks were the most reliable and generalizable designs of the writing assessments. Finally, five decision-making studies (D-studies) in optimization level were conducted and it was indicated that at least four raters (with G-coefficient = 0.80) are necessary for a valid and reliable assessment. Based on these results, to achieve the greatest gain in generalizability, teachers should have their students take two writing assessments and their performance should be rated on at least two scoring methods by at least four raters.

scholarly journals Post Cataract Surgery Refractive Error in Myopic Patients Using SRK/T Versus Holladay 1 Formula for IOL Power Calculation

2019 ◽  
Vol 34 (2) ◽  
Author(s):  
Sidra Anwar, Atif Mansoor Ahmad, Irum Abbas, Zyeima Arif
Keyword(s):  
Intraocular Lens ◽  
Refractive Error ◽  
Axial Length ◽  
Power Calculation ◽  
Mean Error ◽  
Iol Power Calculation ◽  
Group A ◽  
Iol Power ◽  
The Mean ◽  
Group B

Purpose: To compare post-operative mean refractive error with SandersRetzlaff-Kraff/theoretical (SRK-T) and Holladay 1 formulae for intraocular lens (IOL) power calculation in cataract patients with longer axial lengths. Study Design: Randomized controlled trial. Place and Duration of Study: Department of Ophthalmology, Shaikh Zayed Hospital Lahore from 01 January 2017 01 January, 2018. Material and Methods: A total of 80 patients were selected from Ophthalmology Outdoor of Shaikh Zayed Hospital Lahore. The patients were randomly divided into two groups of 40 each by lottery method. IOL power calculation was done in group A using SRK-T formula and in group B using Holladay1 formula after keratomery and A-scan. All patients underwent phacoemulsification with foldable lens implantation. Post-operative refractive error was measured after one month and mean error was calculated and compared between the two groups. Results: Eighty cases were included in the study with a mean age of 55.8 ± 6.2 years. The mean axial length was 25.63 ± 0.78mm, and the mean keratometric power was 43.68 ± 1.1 D. The mean post-operative refractive error in group A (SRK/T) was +0.36D ± 0.33D and in group B (Holladay 1) it was +0.68 ± 0.43. The Mean Error in group A was +0.37D ± 0.31D as compared to +0.69D ± 0.44D in group B. Conclusion: SRK/T formula is superior to Holladay 1 formula for cases having longer axial lengths. Key words: Phacoemulsification, intraocular lens power, longer axial length, biometry.

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