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A Physical Design Strategy on a NoSQL DBMS
Published in Qurban A. Memon, Shakeel Ahmed Khoja, Data Science, 2019
Marcos Jota, Marlene Goncalves, Ritces Parra
To statistically validate our results, statistical tests were performed to determine whether the execution times of the queries on a database in which we apply physical design represent a significant improvement with respect to execution times on a database without physical design. First, we determine whether the resulting execution times for both possibilities (with or without physical design) follow a normal distribution performing a Shapiro–Wilk test [15]. According to Shapiro–Wilk test [15], the execution times obtained in our experiments (samples) can be considered to follow a normal distribution when their p-value is greater than = 0.05. The p-value is a measure of statistical significance that represents the probability of obtaining, by likelihood or chance, a difference as large or greater than that observed, meeting that there is no real difference in the population from which the samples come. It is usually established that if this probability value is less than 5% (0.05), it is sufficiently unlikely to be due to the chance to reject with reasonable certainty our initial hypothesis, and thus, it affirms that the difference is real. If it is greater than 5%, we will not have the necessary confidence to deny that the difference observed is the work of chance.
Exposure levels to various arsenic species and their associated factors in Korean adults
Published in Yong-Guan Zhu, Huaming Guo, Prosun Bhattacharya, Jochen Bundschuh, Arslan Ahmad, Ravi Naidu, Environmental Arsenic in a Changing World, 2019
J.D. Park, I.G. Kang, S.G. Lee, B.S. Choi, H. Kim, H.J. Kwon
Total of 2,044 study subjects, 888 males and 1,156 females were recruited, who were 19 years old or older. They had not been exposed toAs occupationally. We sampled study subjects by probability sampling methods stratified by sex and age from the 102 sampling sites in Korea. Written informed consent was obtained from all study subjects participated in this study. We had conducted 1:1 interviews to investigate demographic characteristics and diet information during the last 24 h. Diet study was performed by the 24-h recall method. Also, we asked whether seafood intake within 72 hours before this study. Then, urine samples were collected and stored at –70°C until As analysis. The speciation analysis of As, such as As(V), As(III), MMA, DMA, arsenobetaine in urine was performed by HPLC-ICP-MS (HPLC pump PerkinElmer Series 200, PerkinElmer NEXION 300S). The levels of various arsenic in urine were presented as arithmetic mean, geometric mean, median and value at 95 percentiles. The concentrations of arsenic in urine were distributed log-normally rather than normal distribution, which were log-transformed for the statistical analyses. And statistical analyses were performed with SAS version 9.2 (SAS institute Inc., Cary, NC, USA). The level of statistical significance was set at p < 0.05.
Involving older adults in design research
Published in Sara J. Czaja, Walter R. Boot, Neil Charness, Wendy A. Rogers, Designing for Older Adults, 2019
Sara J. Czaja, Walter R. Boot, Neil Charness, Wendy A. Rogers
In larger efficacy or effectiveness trials, statistical power is a critical issue as it impacts the confidence that can be placed in the findings of the study. Statistical power is the extent to which the study can detect the difference between two groups and is a function of three factors: the criterion established for statistical significance (alpha level, typically set at .05), the difference that exists between the groups (effect size), and the sample size. Various algorithms and software programs are available to help calculate statistical power and derive needed sample size. Calculation of the appropriate sample size must occur prior to the beginning of the study for planning purposes. In addition to statistical power, the number of participants that will be required impacts the recruitment strategy, staffing requirements, budget, and timeline.
DACov: a deeper analysis of data augmentation on the computed tomography segmentation problem
Published in Computer Methods in Biomechanics and Biomedical Engineering: Imaging & Visualization, 2023
Bruno A. Krinski, Daniel V. Ruiz, Rayson Laroca, Eduardo Todt
The one-sided Wilcoxon signed-rank test was applied to perform a statistical analysis of the data augmentation evaluation. The statistical significance is measured through the P-value, which contains the probability of achieving the measured statistical value when the null hypothesis is true. In order to decide to accept or reject the null hypothesis, a significance level is defined (Demšar 2006). Let represent the difference between the paired samples: , where is the distribution without data augmentation, and is the distribution with data augmentation. Then, if the p-value is higher than , the null hypothesis is accepted (the underlying distribution is stochastically higher than a distribution symmetric about zero), or if the P-value is smaller than , the null hypothesis is rejected.
Dynamic interaction between the human body and the seat during vertical vibration: effect of inclination of the seat pan and the backrest on seat transmissibilities
Published in Ergonomics, 2022
Xiaolu Zhang, Peijin Yu, Yuejuan Li, Yi Qiu, Chao Sun, Zunming Wang, Chi Liu
Fifteen male volunteers (mean age 21.7 year, stature 1.75 m, and weight 70.4 kg) participated in the study (Table 1). The sample size was determined based on that used in previous studies and has shown adequate power to detect statistically significant differences between test conditions (e.g. Basri and Griffin, 2011b; Dewangan et al. 2013; Forta and Schust 2015). Statistical analysis was conducted using SPSS (version 23) with non-parametric statistics. The Wilcoxon matched-pairs signed ranks test was used so as to investigate differences between pairs of conditions. The significance level, indicated by the p value, was taken to indicate statistical significance when it was less than 0.05. All subjects were chosen with no known musculoskeletal disorder. They were instructed to sit in a normal upright posture with hands on their laps and with their backs in contact with the backrest depending on the test conditions (Table 2). A footrest was utilised with the distance of the footrest from the seat adjusted for each subject to give a comfortable sitting posture. The experiment was approved by the Human Experimentation Safety and Ethics Committee at the Beijing University of Technology.
Optimization of Chunk Scheduling Algorithm in Hybrid CDN-P2P Live Video Streaming
Published in IETE Journal of Research, 2018
In order to validate the assumptions that by using the presented approach the QoS parameters will be below set limits, we applied the hypothesis testing method. Testing of the assumption was done using the level of test importance factor α = 0.05 which represents the probability of 5% that the assumption will be null when it is confirmed. Taking into consideration that the tested assumption is based on roof-top values (i.e. that the results will be below standard defined parameter values), we applied the right tailed t test since the sample is less than 30. As the importance level α has been set in advance, we calculated the p-value for all three critical QoS parameters in both experiments as well as other statistical parameters which lead to calculation of the p-value. The p-value is used in the context of assumption testing in order to quantify the idea of statistical significance of evidence. In case that the p-value is higher or equal α, the tested assumption is true [25].