scholarly journals Effective Degrees of Freedom of the Pearson’s Correlation Coefficient under Autocorrelation

2018 ◽  
Author(s):  
Soroosh Afyouni ◽  
Stephen M. Smith ◽  
Thomas E. Nichols
Keyword(s):  
Time Series ◽  
Correlation Coefficient ◽  
Degrees Of Freedom ◽  
Brain Regions ◽  
Resting State Functional Connectivity ◽  
Pearson’S Correlation ◽  
Individual Level ◽  
Human Connectome Project ◽  
Pearson's Correlation ◽  
The Impact

AbstractThe dependence between pairs of time series is commonly quantified by Pearson’s correlation. However, if the time series are themselves dependent (i.e. exhibit temporal autocorrelation), the effective degrees of freedom (EDF) are reduced, the standard error of the sample correlation coefficient is biased, and Fisher’s transformation fails to stabilise the variance. Since fMRI time series are notoriously autocorrelated, the issue of biased standard errors – before or after Fisher’s transformation – becomes vital in individual-level analysis of resting-state functional connectivity (rsFC) and must be addressed anytime a standardized Z-score is computed. We find that the severity of autocorrelation is highly dependent on spatial characteristics of brain regions, such as the size of regions of interest and the spatial location of those regions. We further show that the available EDF estimators make restrictive assumptions that are not supported by the data, resulting in biased rsFC inferences that lead to distorted topological descriptions of the connectome on the individual level. We propose a practical “xDF” method that accounts not only for distinct autocorrelation in each time series, but instantaneous and lagged cross-correlation. We find the xDF correction varies substantially over node pairs, indicating the limitations of global EDF corrections used previously. In addition to extensive synthetic and real data validations, we investigate the impact of this correction on rsFC measures in data from the Young Adult Human Connectome Project, showing that accounting for autocorrelation dramatically changes fundamental graph theoretical measures relative to no correction.

scholarly journals Assessment of the Impact of Selected Satisfaction Parameters on the Competitiveness of Family Tourism

2020 ◽  
pp. 131-143
Author(s):  
Zuzana Goncarova ◽  
Jana Pitekova ◽  
Maria Vrablikova
Keyword(s):  
Correlation Coefficient ◽  
Family Business ◽  
Correlation Matrix ◽  
Family Businesses ◽  
Pearson’S Correlation ◽  
Pearson’S Correlation Coefficient ◽  
Overall Evaluation ◽  
Pearson's Correlation ◽  
Pearson's Correlation Coefficient ◽  
The Impact

The visitor, as the bearer of the demand for tourism services, is primarily a person with his natural desires. For many, a family business is a guarantee of a more helpful approach to meeting clients’ expectations. The paper aims to analyze the dependence between selected parameters of customer satisfaction in two groups of tourist trade establishment or tourism companies. The first group consists of family businesses, which have long shown a higher level of satisfaction compared to traditional tourism companies. The second group is classic tourism companies. In both cases, the research interest is the impact of a change in the assessment of staff and a change in the evaluation of the price/quality ratio on the change in the overall evaluation of these two groups of companies. Authors assumed that satisfaction with the staff in family businesses has a more significant impact on overall satisfaction. The research sample consists of 44 non-family and 18 family businesses. The research includes: assessment of the staff, evaluation of the price/quality ratio and overall evaluation for 2018 and 2020 based on secondary data, calculation of changes (indices) of the parameters as the ratio of values in 2020 to 2018, partial correlation analyzes for individual years and compilation of final correlation matrix, in which is examined the correlation between the change in the overall assessment in family and non-family businesses and the correlation between the change in the price/quality ratio in family and non-family businesses. The basic methods include analysis, synthesis, induction, analogy, comparison, empiricism and Pearson’s correlation coefficient from mathematical-statistical methods. The basic heuristic approach consists of professional literature on the subject matter and secondary sources obtained from the most important accommodation portal booking.com. In the synthesis of knowledge, there are used empirical experience resulting from doing long-term business in the field of tourism of authors. As part of the compilation of the resulting correlation matrix, authors state that in non-family businesses both correlation coefficients are higher than in family ones. In contrast, in evaluating the relationship between the change of personnel, the value of Pearson’s correlation coefficient is higher than 0.7, so it is a strong dependence. Non-family businesses should pay more attention to the human factor. The barrier to fulfillment can be impersonal leadership and inflexible organizational structures. In family businesses, on the other hand, the selection of employees is based on mutual trust. The benefit of the paper is the distinction between family and non-family businesses from the customer’s point of view, which is often a marginalized topic in theory and practice Keywords: competitiveness, correlation, customers´ satisfaction, family business, non-family business, tourism.

scholarly journals Effect of Social Networking Technology Addiction on Academic Performance of University Students in Nigeria

2020 ◽  
Vol 8 (5) ◽  
pp. 173-180 ◽  
Keyword(s):  
Social Media ◽  
Academic Performance ◽  
Social Networking ◽  
Correlation Coefficient ◽  
Well Being ◽  
Pearson’S Correlation ◽  
Pearson’S Correlation Coefficient ◽  
Pearson's Correlation ◽  
Pearson's Correlation Coefficient ◽  
The Impact

The benefits of social media networking platforms on students’ academic performance in contemporary times cannot be, overemphasized. These social networking platforms crafts out opportunities for information sharing andalso danger for students in diverse fields. The danger of social networking addiction on students’ academic performance, health, and social well-being triggered this study.400 students enrolled in this cross-sectional study, through stratified random sampling technique. Using the online survey of Google Form for data collection. The Ordinary Least Square and Pearson’s correlation coefficient was used to quantify and examine the impact. Findingsrevealed that social networking impact significantly on students’ academic performance, and was more prevalent among undergraduate students (P = 0.000). Pearson’s correlation coefficient revealed a significant relationship between social networking addiction, academic performance, health and social well-being of students (p=0.001). The misapplication of social media can become addictive among users and students.Cognitive Behavioral Therapy is proposed to diminish the negative effect of social network addiction on students and other co-users.

scholarly journals Case Study of Anaerobic Digestion Process Stability Detected by Dissolved Hydrogen Concentration

Processes ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 106
Author(s):  
Daniela Platošová ◽  
Jiří Rusín ◽  
Jan Platoš ◽  
Kateřina Smutná ◽  
Roman Buryjan
Keyword(s):  
Anaerobic Digestion ◽  
Correlation Coefficient ◽  
Hydrogen Concentration ◽  
Pearson’S Correlation ◽  
Pearson’S Correlation Coefficient ◽  
Digestion Process ◽  
Short Service Life ◽  
Pearson's Correlation ◽  
Dissolved Hydrogen ◽  
Pearson's Correlation Coefficient

The paper presents the results of a laboratory experiment of mesophilic single-stage anaerobic digestion performed to verify the possibility of early detection of process instability and reactor overload by evaluating the course of dissolved hydrogen concentration of the main intermediate. The digestion process was run in a Terrafors IS rotary drum bioreactor for 230 days. The substrate dosed on weekdays was food leftovers from the university canteen. At an average temperature of 37 °C, an organic loading of volatiles of 0.858 kg m−3 day−1 and a theoretical retention time of 259 days, biogas production of 0.617 Nm3 kg VS−1 was achieved with a CH4 content of 51.7 vol. %. The values of the established FOS/TAC stability indicator ranged from 0.26 to 11.4. The highest value was reached when the reactor was overloaded. The dissolved hydrogen concentration measured by the amperometric microsensor ranged from 0.039–0.425 mg dm−3. Data were statistically processed using Pearson’s correlation coefficient. The correlation of the hydrogen concentration with other parameters such as the concentration of organic acids was evaluated. The value of Pearson’s correlation coefficient was 0.331 and corresponded to a p-value of 0. The results confirmed a very low limit of the hydrogen concentration at which the microbial culture, especially methanogens, was already overloaded. The amperometric microsensor proved to be rather unsuitable for operational applications due to insufficient sensitivity and short service life. The newly designed ratio of dissolved hydrogen concentration to neutralizing capacity was tested but did not work significantly better than the established FOS/TAC stability indicator.

Italian version of the cornell musculoskeletal discomfort questionnaire (CMDQ-I): Translation, cultural adaptation and validation

Work ◽  
2021 ◽  
pp. 1-7
Author(s):  
F. Magnifica ◽  
F. Colagrossi ◽  
A. Aloisi ◽  
S. Politi ◽  
A. Peretti ◽  
...  
Keyword(s):  
Correlation Coefficient ◽  
Cultural Adaptation ◽  
Italian Version ◽  
Cronbach’S Alpha ◽  
Musculoskeletal Discomfort ◽  
Pearson’S Correlation ◽  
Pearson’S Correlation Coefficient ◽  
Cronbach's Alpha ◽  
Pearson's Correlation ◽  
Pearson's Correlation Coefficient

BACKGROUND: Almost 25%of workers in the European Union suffer from back pain, and 23%complain of muscle pain. Sixty-two percent of workers carry out repetitive operations with their hands or arms, 46%work in painful or tired positions and 35%carry or handle loads. OBJECTIVE: This study aimed to translate, culturally adapt and validate the Italian version of the Cornell Musculoskeletal Discomfort Questionnaire (CMDQ-I). METHODS: Translation and cultural adaptation procedures followed international guidelines. Participants were recruited from among the personnel components of the Italian Air Force, who were between 18 and 65 years old. Cronbach’s alpha and the intraclass correlation coefficient (ICC) were calculated to assess internal consistency and stability, respectively. The CDMQ-I was administered together with the Visual Analogic Scale (VAS), and the validity was evaluated using Pearson’s correlation coefficient. RESULTS: All CDMQ-I items were either identical or similar in meaning to the original version’s items. The scale was administered twice with a retest after seven to 10 days to 66 participants. Cronbach’s alpha was higher than 0.761, and the ICC ranged between 0.737 and 0.952. Pearson’s correlation coefficient showed positive and significant correlations (p >  0.01). CONCLUSIONS: The study produced an Italian version of the CMDQ with good reliability and validity. This scale is a useful tool to investigate the frequency and intensity of musculoskeletal disorders in various categories of workers.

scholarly journals Suitable Docking Protocol for the Design of Novel Coumarin Derivatives with Selective MAO-B Effects

2021 ◽  
Vol 1 (1) ◽  
pp. 40-47
Author(s):  
Emilio Viktorov Mateev ◽  
Iva Valkova ◽  
Maya Georgieva ◽  
Alexander Zlatkov
Keyword(s):  
Correlation Coefficient ◽  
Scoring Functions ◽  
Pearson’S Correlation ◽  
Chain Flexibility ◽  
Pearson’S Correlation Coefficient ◽  
Pairwise Correlation ◽  
Mao B ◽  
Docking Protocol ◽  
Pearson's Correlation ◽  
Pearson's Correlation Coefficient

Recently, the application of molecular docking is drastically increasing due to the rapid growth of resolved crystallographic receptors with co-crystallized ligands. However, the inability of docking softwares to correctly score the occurred interactions between ligands and receptors is still a relevant issue. This study examined the Pearson’s correlation coefficient between the experimental monoamine oxidase-B (MAO-B) inhibitory activity of 44 novel coumarins and the obtained GOLD 5.3 docking scores. Subsequently, optimization of the docking protocol was carried out to achieve the best possible pairwise correlation. Numerous modifications in the docking settings such as alteration in the scoring functions, size of the grid space, presence of active waters, and side-chain flexibility were conducted. Furthermore, ensemble docking simulations into two superimposed complexes were performed. The model was validated with a test set. A significant Pearson’s correlation coefficient of 0.8217 was obtained for the latter. In the final stage of our work, we observed the major interactions between the top-scored ligands and the active site of 1S3B.

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