Incorporating Uncertainty Into Parallel Analysis for Choosing the Number of Factors via Bayesian Methods     

Roy Levy  Yan Xia  Samuel B. Green 《Educational and psychological measurement》2021,81(3):466

A number of psychometricians have suggested that parallel analysis (PA) tends to yield more accurate results in determining the number of factors in comparison with other statistical methods. Nevertheless, all too often PA can suggest an incorrect number of factors, particularly in statistically unfavorable conditions (e.g., small sample sizes and low factor loadings). Because of this, researchers have recommended using multiple methods to make judgments about the number of factors to extract. Implicit in this recommendation is that, when the number of factors is chosen based on PA, uncertainty nevertheless exists. We propose a Bayesian parallel analysis (B-PA) method to incorporate the uncertainty with decisions about the number of factors. B-PA yields a probability distribution for the various possible numbers of factors. We implement and compare B-PA with a frequentist approach, revised parallel analysis (R-PA), in the contexts of real and simulated data. Results show that B-PA provides relevant information regarding the uncertainty in determining the number of factors, particularly under conditions with small sample sizes, low factor loadings, and less distinguishable factors. Even if the indicated number of factors with the highest probability is incorrect, B-PA can show a sizable probability of retaining the correct number of factors. Interestingly, when the mode of the distribution of the probabilities associated with different numbers of factors was treated as the number of factors to retain, B-PA was somewhat more accurate than R-PA in a majority of the conditions.  相似文献   

Working Together: Integrating Computational Modeling Approaches to Investigate Complex Phenomena     

Bielik  Tom  Fonio  Ehud  Feinerman  Ofer  Duncan  Ravit Golan  Levy  Sharona T. 《Journal of Science Education and Technology》2021,30(1):40-57

Journal of Science Education and Technology - Complex systems are made up of many entities, whose interactions emerge into distinct collective patterns. Computational modeling platforms can provide...  相似文献   

Gender and IT in the Household: Evolving Patterns of Internet Use in the United States   总被引：1，自引：0，他引：1  

Ruby Roy Dholakia 《The Information Society》2006,22(4):231-240

Information technology (IT)—computers and related technologies—is the latest technology to enter the household. Like other technologies, gender is a major factor in its adoption and use as well as its perceived usefulness. Unlike prior household technologies, the computer's entry into the household has followed a different pattern. Early statistics revealed a vast gender divide, with men using computers and related technologies much more in the household. More recent statistics show a narrowing of the divide, perhaps even a reversal, particularly in the United States, with women outnumbering men in the access to and use of the Internet. In this article, the role of gender and its relationship with Internet use in the home are reviewed. In addition to overall adoption and access, the review focuses on specific Internet applications and examines the factors that contribute to gender differences in adoption and use of computers and Internet applications in the home.  相似文献   

Reconvene and Reconnect the Antioxidant Hypothesis in Human Health and Disease     

Singh PP  Chandra A  Mahdi F  Roy A  Sharma P 《Indian journal of clinical biochemistry : IJCB》2010,25(3):225-243

The antioxidants are essential molecules in human system but are not miracle molecules. They are neither performance enhancers nor can prevent or cure diseases when taken in excess. Their supplemental value is debateable. In fact, many high quality clinical trials on antioxidant supplement have shown no effect or adverse outcomes ranging from morbidity to all cause mortality. Several Chochrane Meta-analysis and Markov Model techniques, which are presently best available statistical models to derive conclusive answers for comparing large number of trials, support these claims. Nevertheless none of these statistical techniques are flawless. Hence, more efforts are needed to develop perfect statistical model to analyze the pooled data and further double blind, placebo controlled interventional clinical trials, which are gold standard, should be implicitly conducted to get explicit answers. Superoxide dismutase (SOD), glutathione peroxidase and catalase are termed as primary antioxidants as these scavenge superoxide anion and hydrogen peroxide. All these three enzymes are inducible enzymes, thereby inherently meaning that body increases or decreases their activity as per requirement. Hence there is no need to attempt to manipulate their activity nor have such efforts been clinically useful. SOD administration has been tried in some conditions especially in cancer and myocardial infarction but has largely failed, probably because SOD is a large molecule and can not cross cell membrane. The dietary antioxidants, including nutrient antioxidants are chain breaking antioxidants and in tandem with enzyme antioxidants temper the reactive oxygen species (ROS) and reactive nitrogen species (RNS) within physiological limits. Since body is able to regulate its own requirements of enzyme antioxidants, the diet must provide adequate quantity of non-enzymic antioxidants to meet the normal requirements and provide protection in exigent condition. So far, there is no evidence that human tissues ever experience the torrent of reactive species and that in chronic conditions with mildly enhanced generation of reactive species, the body can meet them squarely if antioxidants defense system in tissues is biochemically optimized. We are not yet certain about optimal levels of antioxidants in tissues. Two ways have been used to assess them: first by dietary intake and second by measuring plasma levels. Lately determination of plasma/serum level of antioxidants is considered better index for diagnostic and prognostic purposes. The recommended levels for vitamin A, E and C and beta carotene are 2.2–2.8 μmol/l; 27.5–30 μmol/l; 40–50 μmol/l and 0.4–0.5 μmol/l, respectively. The requirement and recommended blood levels of other dietary antioxidants are not established. The resolved issues are (1) essential to scavenge excess of radical species (2) participants in redox homeostasis (3) selective antioxidants activity against radical species (4) there is no universal antioxidant and 5) therapeutic value in case of deficiency. The overarching issues are (1) therapeutic value as adjuvant therapy in management of diseases (2) supplemental value in developing population (3) selective interactivity of antioxidant in different tissues and on different substrates (4) quantitative contribution in redox balance (5) mechanisms of adverse action on excess supplementation (6) advantages and disadvantages of prooxidant behavior of antioxidants (7) behavior in cohorts with polymorphic differences (8) interaction and intervention in radiotherapy, diabetes and diabetic complications and cardiovascular diseases (9) preventive behavior in neurological disorders (10) benefits of non-nutrient dietary antioxidants (11) markers to assess optimized antioxidants status (12) assessment of benefits of supplementation in alcoholics and heavy smokers. The unresolved and intriguing issues are (1) many compounds such as vitamin A and many others possessing both antioxidant and non-antioxidant properties contribute to both the activities in vivo or exclusively only to non-antioxidant activity and (2) since human tissues do not experience the surge of FR, whether there is any need to develop stronger synthetic antioxidants. Theoretically such antioxidants may do more harm than good.  相似文献   

A note on quasi-static thermal deflection of a thin clamped circular plate due to ramp-type heating of a concentric circular region of the upper face     

Snehanshu Kumar Roy Choudhuri 《Journal of The Franklin Institute》1973,296(3):213-219

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Story of fission     

Amit Roy 《Resonance》2016,21(3):247-258

The discovery of nuclear fission is the culmination of sustained efforts involving many scientists led by Hahn and Meitner to understand the production of artificial radioactivity induced by neutrons bombarding uranium. The large energy release in this process was almost immediately used for both military and civilian purposes. It also started the largescale funding of scientific research by governments across the world. Nuclear energy is one of the clean sources of energy and contributes very little to global warming.  相似文献   

Are Letter Detection and Proofreading Tasks Equivalent?     

Jean Saint-Aubin  Marie-Claire Losier  Macha Roy  Mike Lawrence 《Scientific Studies of Reading》2015,19(2):145-165

When readers search for misspellings in a proofreading task or for a letter in a letter detection task, they are more likely to omit function words than content words. However, with misspelled words, previous findings for the letter detection task were mixed. In two experiments, the authors tested the functional equivalence of both tasks. Results reveal similar patterns of omissions for both search tasks when misspellings were produced by substituting one letter for another: There were more omissions for function words than for content words. However, when two letters were transposed, differences between the two tasks emerged. It is possible to conclude that letter detection and proofreading are based on common cognitive processes but the nature of the target can modulate the effects. Results are interpreted in light of the attentional disengagement model and the guidance organization model of the missing-letter effect.  相似文献   

Relationship between foot strike pattern,running speed,and footwear condition in recreational distance runners     

Roy T. H. Cheung  Rodney Y. L. Wong  Tim K. W. Chung  R. T. Choi  Wendy W. Y. Leung  Diana H. Y. Shek 《Sports biomechanics / International Society of Biomechanics in Sports》2017,16(2):238-247

Compared to competitive runners, recreational runners appear to be more prone to injuries, which have been associated with foot strike patterns. Surprisingly, only few studies had examined the foot strike patterns outside laboratories. Therefore, this study compared the foot strike patterns in recreational runners at outdoor tracks with previously reported data. We also investigated the relationship between foot strike pattern, speed, and footwear in this cohort. Among 434 recreational runners analysed, 89.6% of them landed with rearfoot strike (RFS). Only 6.9 and 3.5% landed with midfoot and forefoot, respectively. A significant shift towards non-RFS was observed in our cohort, when compared with previously reported data. When speed increased by 1 m/s, the odds of having forefoot strike and midfoot strike relative to RFS increased by 2.3 times and 2.6 times, respectively. Runners were 9.2 times more likely to run with a forefoot strike in minimalists compared to regular running shoes, although 70% of runners in minimalists continued to use a RFS. These findings suggest that foot strike pattern may differ across running conditions and runners should consider these factors in order to mitigate potential injury.  相似文献   

Borders and Intersections of Possibility: Multilingual Repertoires of Refugee Families in the Southwest U.S.     

Laura A. Roy 《Multicultural Perspectives》2015,17(2):61-68

This study examines the linguistic and cultural intersections of recently arrived Somali Bantu refugee students in South Texas through the lens of border theory. The use of Spanish in the homes of refugee families is explored in addition to ways in which an educator used testimonios to honor students’ migration experiences. Findings show how specific approaches used in schools that affirm both the receiving communities’ and the new arrivals' local knowledge can have a lasting impact on literacy acquisition and resettlement experiences. Findings from this study also illuminate the potential impact of educators who develop a critical, inquiry stance by embedding multiple entry points for students to cross social, cultural, linguistic, and curricular borders in school.  相似文献   

Spectral and graph-theoretic bounds on steady-state-probability estimation performance for an ergodic Markov chain     

Mengran Xue  Sandip Roy 《Journal of The Franklin Institute》2011,348(9):2448-2467

Motivated by the wide application of Markov-chain steady-state-probability estimation, we pursue a spectral and graph-theoretic performance analysis of a classical estimator for steady-state probabilities here. Specifically, we connect a performance measure to estimate the structure of the underlying graph defined on the Markov-chain's state transitions. To do so, (1) we present a series of upper bounds on the performance measure in terms of the subdominant eigenvalue of the state transition matrix, which is closely connected with the graph structure; (2) as an illustration of the graph-theoretic analysis, we then relate the subdominant eigenvalue to the connectivity of the graph, including for the strong-connectivity case and the weak-link case. We also apply the results to characterize estimation in Markov chains with rewards.  相似文献