Total Variance
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2022 ◽  
Vol 269 ◽  
pp. 112806
Stephen V. Stehman ◽  
John Mousoupetros ◽  
Ronald E. McRoberts ◽  
Erik Næsset ◽  
Bruce W. Pengra ◽  

2021 ◽  
Vol 18 (4) ◽  
pp. 213-222
Edgardo Cayón Fallon ◽  
Julio Sarmiento

In times of exogenous systemic shocks, such as the COVID-19 pandemic, it is important to identify hedge or safe haven assets. Therefore, this paper analyzes changes in the idiosyncratic risk of Bitcoin in a portfolio of commodities and global stocks. For this purpose, the M-GARCH model employed considers the interdependence among all the portfolio assets by using a time-varying asset pricing framework. This framework measures the impact of commodities and global stock prices as sources of systemic risk for Bitcoin returns before and after the COVID-19 pandemic. The evidence suggests that during the COVID-19 pandemic, the effects of changes in commodities and global prices on the idiosyncratic risk of Bitcoin were statistically significant. The idiosyncratic risk of Bitcoin measured as a percentage of total variance not accounted for by the proposed model rose from 86.06% to 95.05% during the pandemic. These results are in line with previous studies regarding the properties of Bitcoin as a hedge or safe haven asset for a portfolio composed of commodities and global stocks.

2021 ◽  
Vol 11 (5) ◽  
pp. 129-142
Cristobal Coaguila Berly David ◽  
Barriga Paria Christ Jesus

The purpose of this research work is to optimize the occupational health and safety protocol by increasing distancing and mitigating physical contact to prevent the spread of Covid-19, using QR catches to identify personnel. Contrasting the sanitary measures to protect the health and integrity of the personnel of the operations area of the Tailing Disposal System -Quellaveco project. For the study of the database, factor analysis is used as a multivalent statistical method, with this method the number of 997 daily reports was analyzed, addressing the study of the structure of correlations between a large number of variables, factor analysis assists in the selection of a representative subgroup of variables and creates new variables called factors, when performing the analysis and treatment of 24 variables with the SPSS 25 software, the variables with the correlation matrix were reduced to 13, and with the total variance explained, a matrix different from that of identity was defined, reducing the dimensionality of the problem from 13 to 5 factors.

2021 ◽  
pp. 0013189X2110513
Joseph A. Taylor ◽  
Terri Pigott ◽  
Ryan Williams

Toward the goal of more rapid knowledge accumulation via better meta-analyses, this article explores statistical approaches intended to increase the precision and comparability of effect sizes from education research. The featured estimate of the proposed approach is a standardized mean difference effect size whose numerator is a mean difference that has been adjusted for baseline differences in the outcome measure, at a minimum, and whose denominator is the total variance. The article describes the utility and efficiency of covariate adjustment through baseline measures and the need to standardize effects on a total variance that accounts for variation at multiple levels. As computation of the total variance can be complex in multilevel studies, a shiny application is provided to assist with computation of the total variance and subsequent effect size. Examples are provided for how to interpret and input the required calculator inputs.

Stavros Kyriakidis ◽  
Matthew Stevens ◽  
Kristina Karstad ◽  
Karen Søgaard ◽  
Andreas Holtermann

The purpose of our study was to investigate which organizational levels and factors determine the number of resident handlings in eldercare. We conducted a multi-level study, stratified on day and evening shifts, including information on four levels: nursing homes (n = 20), wards within nursing homes (day, n = 120; evening, n = 107), eldercare workers within wards (day, n = 619; evening, n = 382), and within eldercare workers (i.e., days within eldercare workers; day, n = 5572; evening, n = 2373). We evaluated the influence of each level on the number of resident handlings using variance components analysis and multivariate generalized linear mixed models. All four levels contributed to the total variance in resident handlings during day and evening shifts, with 13%/20% at “nursing homes”, 21%/33% at “wards within nursing homes”, 25%/31% at “elder-care workers within wards”, and 41%/16% “within eldercare workers”, respectively. The percentage of residents with a higher need for physical assistance, number of residents per shift, occupational position (only within day shifts), and working hours per week (only within day shifts) were significantly associated with the number of resident handlings performed per shift. Interventions aiming to modify number of resident handlings in eldercare ought to target all levels of the eldercare organization.

2021 ◽  
Vol 17 (11) ◽  
pp. 48
Yap Jing Xuan ◽  
Muhammad Asyraf Che Amat

Recent evidence indicates an elevated risk of social media addiction in university students. This research was designed to enhance the understanding of social media addiction among university students by investigating the relationships between self-esteem, life satisfaction, and social media addiction, with the possibility of gender differences in the relationships. 288 university students (103 males, 185 females) from the Faculty of Educational Studies at Universiti Putra Malaysia (UPM) done the Social Media Addiction, Rosenberg Self-Esteem (RSES), and Life Satisfaction Scales. Results showed that self-esteem and life satisfaction accounted for 64% of the total variance in social media addiction. Life satisfaction was a significant factor in increasing the possibility of social media addiction. On the contrary, there were no significant differences in life satisfaction and self-esteem, the latter exhibited no association with social media addiction. Furthermore, males were much more addicted to social media than females. An understanding on gender differences may be helpful for clinicians to expand suitable therapy by taking into account these findings, meanwhile, the statistically significant differences between the variables may contribute to predict student addiction levels in social media. The results of this study are obtained from Malaysian university students and possible generalisation to other populations should be verified by further studies.

E O’ Connor ◽  
F M McGovern ◽  
D T Byrne ◽  
T M Boland ◽  
E Dunne ◽  

Abstract Portable accumulation chambers (PAC) enable gaseous emissions from small ruminants to be measured over a 50 min period, to date however, the repeatability of consecutive days of measurement in the PAC has not been investigated. The objectives of this study were to investigate: 1) the repeatability of consecutive days of gaseous measurements in the PAC, 2) the number of days required to achieve precise gaseous measurements, and 3) to develop a prediction equation for gaseous emissions in sheep. A total of 48 ewe lambs (c. 10 to 11 mo of age) were randomly divided into four measurement groups each day, for 17 consecutive days. Gaseous measurements were conducted between 0800 h and 1200 h daily. Animals were removed from perennial ryegrass silage for at least 1 h before measurements in the PAC and animals were assigned randomly to each of the 12 chambers. Methane (CH4; ppm) concentration, oxygen (O2; percentage) and carbon dioxide (CO2; percentage) were measured at 3 time points (0, 25, and 50 min after entry of the first animal into the first chamber). To quantify the effect of animal and day variation on gaseous emissions, between-animal, between-day and error variances were calculated for each gaseous measurement using a linear mixed model. The number of days required to gain a certain precision (defined as the 95% confidence interval (CI) range) for each gaseous measurement was also calculated. For all 3 gases the between-day variance (39% to 40%) accounted for a larger proportion of total variance compared to between-animal variance, while the repeatability of 17 consecutive days of measurement was 0.36, 0.31 and 0.23 for CH4, CO2 and O2, respectively. Correlations between consecutive days of measurement were strong for all 3 gases; the strongest correlation between d 1 and the remaining days for CH4, CO2 and O2 was 0.71 (d 1 and d 6), 0.77 (d 1 and d 2) and 0.83 (d 1 and d 5), respectively. A high level of precision was achieved when gaseous measurements from PAC were taken over 3 consecutive days. The prediction equation over-estimated gaseous production for all 3 gases: the correlations between actual and predicted gaseous output ranged from 0.67 to 0.71, with the r 2 ranging from 0.45 to 0.71. Results from this study will aid the refinement of the protocol for the measurement of gaseous emissions in sheep using the PAC.

2021 ◽  
Vol 79 (5) ◽  
pp. 767-780
Pinar Mert

Women expose to barriers in their work-life that are not stated clearly. Although these invisible barriers occur in many sectors, they are common in the education sector. So, this study aimed to reveal the relation between the paternalistic leadership displayed by principals in traditional collectivist cultures and the glass ceiling syndrome experienced by female teachers. For this reason, the correlation survey model was used in the research. Female teachers living in Istanbul were selected with the appropriate sampling method due to the Covid 19 outbreak. “The Paternal Leadership Behaviors Scale of School Principals” and “Glass Ceiling Syndrome Scale for Female Teachers” were applied to 358 female teachers. Applied t-test, correlation, ANOVA, and regression analysis. As a result of statistical analysis, it saw that the benevolent, moral, authoritarian, and exploitative leadership behaviors perceived by teachers significantly predicted the perceptions of glass ceiling syndrome. Although benevolent, moral, authoritarian, exploitative paternalistic leadership behaviors mainly indicated teachers' perception of the glass ceiling, they were even low. Especially authoritarian and exploitative paternalistic leadership behaviors explained 5% of the total variance in teachers' perception of the glass ceiling syndrome. Keywords: glass ceiling syndrome, paternalistic leadership, female teachers, correlation survey model

2021 ◽  
Vol 13 (19) ◽  
pp. 11105
Hyun-Jeong Lee ◽  
Yoon-Seo Hwang

In Korea, the housing issues faced by young renters negatively impact both their parents and themselves. This study aimed at exploring young renters’ situations whereby they receive financial support from their parents in order to pay current housing expenses, and their perception of housing cost burdens. Additionally, this study examined the influences on the reception of parental support and their perceived housing cost burdens. In February and March of 2021, an online questionnaire survey was conducted amongst young renters living independently from their parents and 385 responses from Jeonse renters and monthly renters with deposits in private rental housing units were analyzed. The major findings are as follows: (1) among the subjects, 43.4% had experienced receiving parental support in order to pay for housing expenses since their first instance of independent living, and 35.6% were still receiving parental support. (2) A discriminant model with a linear combination of the variables of age, income, residential location and rental deposit was found effective in predicting the receipt of parental support with 66.5% accuracy. (3) A linear combination of the variables of gender, rental deposit and monthly cash housing expenses was found to explain 5.8% of the total variance of perceived housing cost burdens. The results imply the necessity to expand the provision of public housing and housing subsidies to alleviate the financial burdens of young renters and their parents.

2021 ◽  
Vol 11 (1) ◽  
Ali Khodi

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.

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