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Statistics in Medicine Jan 2024Accurate assessment of the mean-variance relation can benefit subsequent analysis in biomedical research. However, in most biomedical data, both the true mean and the...
Accurate assessment of the mean-variance relation can benefit subsequent analysis in biomedical research. However, in most biomedical data, both the true mean and the true variance are unavailable. Instead, raw data are typically used to allow forming sample mean and sample variance in practice. In addition, different experimental conditions sometimes cause a slightly different mean-variance relation from the majority of the data in the same data set. To address these issues, we propose a semiparametric estimator, where we treat the uncertainty in the sample mean as a measurement error problem, the uncertainty in the sample variance as model error, and use a mixture model to account for different mean-variance relations. Asymptotic normality of the proposed method is established and its finite sample properties are demonstrated by simulation studies. The data application shows that the proposed method produces sensible results compared with methods either ignoring the uncertainty in the sample means or ignoring the potential different mean-variance relations.
Topics: Humans; Models, Statistical; Computer Simulation; Uncertainty
PubMed: 37994214
DOI: 10.1002/sim.9970 -
Conservation Biology : the Journal of... Feb 2023Restoration of foundation species promises to reverse environmental degradation and return lost ecosystem services, but a lack of standardized evaluation across projects... (Meta-Analysis)
Meta-Analysis Review
Restoration of foundation species promises to reverse environmental degradation and return lost ecosystem services, but a lack of standardized evaluation across projects limits understanding of recovery, especially in marine systems. Oyster reefs are restored to reverse massive global declines and reclaim valuable ecosystem services, but the success of these projects has not been systematically and comprehensively quantified. We synthesized data on ecosystem services associated with oyster restoration from 245 pairs of restored and degraded reefs and 136 pairs of restored and reference reefs across 3500 km of U.S. Gulf of Mexico and Atlantic coastlines. On average, restoration was associated with a 21-fold increase in oyster production (mean log response ratio = 3.08 [95% confidence interval: 2.58-3.58]), 34-97% enhancement of habitat provisioning (mean community abundance = 0.51 [0.41-0.61], mean richness = 0.29 [0.19-0.39], and mean biomass = 0.69 [0.39-0.99]), 54% more nitrogen removal (mean = 0.43 [0.13-0.73]), and 89-95% greater sediment nutrients (mean = 0.67 [0.27-1.07]) and organic matter (mean = 0.64 [0.44-0.84]) relative to degraded habitats. Moreover, restored reefs matched reference reefs for these ecosystem services. Our results support the continued and expanded use of oyster restoration to enhance ecosystem services of degraded coastal systems and match many functions provided by reference reefs.
Topics: Animals; Ecosystem; Conservation of Natural Resources; Ostreidae; Seafood
PubMed: 35686509
DOI: 10.1111/cobi.13966 -
Physical Review. E Oct 2023The notion of mean temperature is crucial for a number of fields, including climate science, fluid dynamics, and biophysics. However, so far its correct thermodynamic...
The notion of mean temperature is crucial for a number of fields, including climate science, fluid dynamics, and biophysics. However, so far its correct thermodynamic foundation is lacking or even believed to be impossible. A physically correct definition should not be based on mathematical notions of the means (e.g., the mean geometric or mean arithmetic), because they are not unique, and they ignore the fact that temperature is an ordinal level variable. We offer a thermodynamic definition of the mean temperature that is based upon the following two assumptions. First, the correct definition should necessarily involve equilibration processes in the initially nonequilibrium system. Among such processes, reversible equilibration and fully irreversible equilibration are the two extreme cases. Second, within the thermodynamic approach we assume that the mean temperature is determined mostly by energy and entropy. Together with the dimensional analysis, the two assumptions lead to a definition of the mean temperature that is determined up to a weight factor that can be fixed to 1/2 due to the maximum ignorance principle. The mean temperature for ideal and (van der Waals) nonideal gases with temperature-independent heat capacity is given by a general and compact formula that (besides the initial temperatures) only depends on the heat capacities and concentration of gases. Our method works for any nonequilibrium initial state, not only two-temperature states.
PubMed: 37978650
DOI: 10.1103/PhysRevE.108.044112 -
Tanaffos Jan 2023Mean platelet volume (MPV) reflects the platelet production rate and stimulation, while mean corpuscular volume (MCV) represents the average size of red blood cells....
BACKGROUND
Mean platelet volume (MPV) reflects the platelet production rate and stimulation, while mean corpuscular volume (MCV) represents the average size of red blood cells. Considering the possibility of the relationship between red cell index changes and different severities of chronic obstructive pulmonary disease (COPD) as well as the uncertainty of the available results in this regard, the present study aimed at evaluating the relationship between MPV and MCV in the outcome of patients with acute exacerbation of COPD (AECOPD).
MATERIALS AND METHODS
In this cross-sectional analytical study, 150 patients with AECOPD that referred to the emergency department (ED) were included in the study. The severity of the disease was recorded using the GOLD classification, and the MPV and the MCV were evaluated based on the reference range of kits in the laboratory. Then, the data were analyzed using SPSS software.
RESULTS
The mean MPV and MCV were 9.7±8.3 and 85.9±11.5, respectively, and had no significant difference in different severities of COPD(P>0.05). Moreover, although MCV in survivals with a mean of 88.81±6.47 was higher than that of non-survivals with a mean of 85.77±11.73, and MPV in the non-survivals with a mean of 8.53±9.74 was higher than that of survivals with the mean of 8.86±0.92, this difference was not statistically significant (P>0.05).
CONCLUSION
Overall, the results of this study showed that the mean MPV and MCV did not have any significant relationship with AECOPD and patient outcome.
PubMed: 37920314
DOI: No ID Found -
Vision Research Feb 2020When there are many visual items, the visual system could represent their summary statistics (e.g., mean, variance) to process them efficiently. Although many previous...
When there are many visual items, the visual system could represent their summary statistics (e.g., mean, variance) to process them efficiently. Although many previous studies have investigated the mean or variance representation itself, a relationship between these two ensemble representations has not been investigated much. In this study, we tested the potential interaction between mean and variance representations by using a visual adaptation method. We reasoned that if mean and variance representations interact with each other, an adaptation aftereffect to either mean or variance would influence the perception of the other. Participants watched a sequence of orientation arrays containing a specific statistical property during the adaptation period. To produce an adaptation aftereffect specific to variance or mean, one property of the adaptor arrays (variance or mean) had a fixed value while the other property was randomly varied. After the adaptation, participants were asked to discriminate the property of the test array that was randomly varied during the adaptation. We found that the adaptation aftereffect of orientation variance influenced the sensitivity of mean orientation discrimination (Experiment 1), and that the adaptation aftereffect of mean orientation influenced the bias of orientation variance discrimination (Experiment 2). These results suggest that mean and variance representations do closely interact with each other. Considering that mean and variance reflect the representative value and dispersion of multiple items respectively, the interactions between mean and variance representations may reflect their complementary roles to summarize complex visual information effectively.
Topics: Adaptation, Ocular; Female; Figural Aftereffect; Humans; Male; Orientation, Spatial; Psychophysics; Visual Perception
PubMed: 31954877
DOI: 10.1016/j.visres.2020.01.002 -
IEEE Transactions on Cybernetics Oct 2021Multiagent reinforcement learning (MARL) has recently attracted considerable attention from both academics and practitioners. Core issues, e.g., the curse of...
Multiagent reinforcement learning (MARL) has recently attracted considerable attention from both academics and practitioners. Core issues, e.g., the curse of dimensionality due to the exponential growth of agent interactions and nonstationary environments due to simultaneous learning, hinder the large-scale proliferation of MARL. These problems deteriorate with an increased number of agents. To address these challenges, we propose an adversarial collaborative learning method in a mixed cooperative-competitive environment, exploiting friend-or-foe Q-learning and mean-field theory. We first treat neighbors of agent i as two coalitions ( i 's friend and opponent coalition, respectively), and convert the Markov game into a two-player zero-sum game with an extended action set. By exploiting mean-field theory, this new game simplifies the interactions as those between a single agent and the mean effects of friends and opponents. A neural network is employed to learn the optimal mean effects of these two coalitions, which are trained via adversarial max and min steps. In the max step, with fixed policies of opponents, we optimize the friends' mean action to maximize their rewards. In the min step, the mean action of opponents is trained to minimize the friends' rewards when the policies of friends are frozen. These two steps are proved to converge to a Nash equilibrium. Then, another neural network is applied to learn the best response of each agent toward the mean effects. Finally, the adversarial max and min steps can jointly optimize the two networks. Experiments on two platforms demonstrate the learning effectiveness and strength of our approach, especially with many agents.
PubMed: 33095725
DOI: 10.1109/TCYB.2020.3025491 -
Attention, Perception & Psychophysics Oct 2022The mean estimation task, which explicitly asks observers to estimate the mean feature value of multiple stimuli, is a fundamental paradigm in research areas such as...
The mean estimation task, which explicitly asks observers to estimate the mean feature value of multiple stimuli, is a fundamental paradigm in research areas such as ensemble coding and cue integration. The current study uses computational models to formalize how observers summarize information in mean estimation tasks. We compare model predictions from our Fidelity-based Integration Model (FIM) and other models on their ability to simulate observed patterns in within-trial weight distribution, across-trial information integration, and set-size effects on mean estimation accuracy. Experiments show non-equal weighting within trials in both sequential and simultaneous mean estimation tasks. Observers implicitly overestimated trial means below the global mean and underestimated trial means above the global mean. Mean estimation performance declined and stabilized with increasing set sizes. FIM successfully simulated all observed patterns, while other models failed. FIM's information sampling structure provides a new way to interpret the capacity limit in visual working memory and sub-sampling strategies. As a model framework, FIM offers task-dependent modeling for various ensemble coding paradigms, facilitating research synthesis across different studies in the literature.
Topics: Humans; Memory, Short-Term; Visual Perception
PubMed: 35199324
DOI: 10.3758/s13414-021-02410-1 -
BJR Open 2023The objective of this review was to examine the impact of previous mammogram availability on radiologists' performance from screening populations and experimental... (Review)
Review
OBJECTIVE
The objective of this review was to examine the impact of previous mammogram availability on radiologists' performance from screening populations and experimental studies.
MATERIALS AND METHODS
A search of the literature was conducted using five databases: MEDLINE, PubMed, Web of Science, ScienceDirect, and CINAHL as well as Google and reference lists of articles. Keywords were combined with "AND" or "OR" or "WITH" and included "prior mammograms, diagnostic performance, initial images, diagnostic efficacy, subsequent images, previous imaging, and radiologist's performance". Studies that assessed the impact of previous mammogram availability on radiologists' performance were reviewed. The Standard for Reporting Diagnostic Accuracy guidelines was used to critically appraise individual sources of evidence.
RESULTS
A total of 15 articles were reviewed. The sample of mammogram cases used across these studies varied from 36 to 1,208,051. Prior mammograms did not affect sensitivity [with priors: 62-86% (mean = 73.3%); without priors: 69.4-87.4% (mean = 75.8%)] and cancer detection rate, but increased specificity [with priors: 72-96% (mean = 87.5%); without priors: 63-87% (mean = 80.5%)] and reduced false-positive rates [with priors: 3.7 to 36% (mean = 19.9%); without priors 13.3-49% (mean = 31.4%)], recall rates [with priors: 3.8-57% (mean = 26.6%); without priors: [4.9%-67.5% (mean = 37.9%)], and abnormal interpretation rate decreased by 4% with priors. Evidence for the associations between the availability of prior mammograms and positive-predictive value, area under the curve (AUC) from the receiver operating characteristic curve (ROC) and localisation ROC AUC, and positive-predictive value of recall is limited and unclear.
CONCLUSION
Availability of prior mammograms reduces recall rates, false-positive rates, abnormal interpretation rates, and increases specificity without affecting sensitivity and cancer detection rate.
PubMed: 37942498
DOI: 10.1259/bjro.20230038 -
Journal of Neurosurgery. Pediatrics Apr 2020Combined metopic-sagittal craniosynostosis is traditionally treated with open cranial vault remodeling and fronto-orbital advancement, sometimes in multiple operations....
OBJECTIVE
Combined metopic-sagittal craniosynostosis is traditionally treated with open cranial vault remodeling and fronto-orbital advancement, sometimes in multiple operations. Endoscopic treatment of this multisuture synostosis presents a complex challenge for the surgeon and orthotist.
METHODS
The authors retrospectively analyzed the preoperative and 1-year postoperative CT scans of 3 patients with combined metopic-sagittal synostosis, all of whom were treated with simultaneous endoscope-assisted craniectomy of the metopic and sagittal sutures followed by helmet therapy. Established anthropometric measurements were applied to assess pre- and postoperative morphology, including cranial index and interfrontal divergence angle (IFDA). Patients' measurements were compared to those obtained in 18 normal controls.
RESULTS
Two boys and one girl underwent endoscope-assisted craniectomy at a mean age of 81 days. The mean preoperative cranial index was 0.70 (vs control mean of 0.82, p = 0.009), corrected postoperatively to a mean of 0.82 (vs control mean of 0.80, p = 0.606). The mean preoperative IFDA was 110.4° (vs control mean of 152.6°, p = 0.017), corrected postoperatively to a mean of 139.1° (vs control mean of 140.3°, p = 0.348). The mean blood loss was 100 mL and the mean length of stay was 1.7 days. No patient underwent reoperation. The mean clinical follow-up was 3.4 years.
CONCLUSIONS
Endoscope-assisted craniectomy with helmet therapy is a viable single-stage treatment option for combined metopic-sagittal synostosis, providing correction of the stigmata of trigonoscaphocephaly, with normalization of the cranial index and IFDA.
PubMed: 32302979
DOI: 10.3171/2020.2.PEDS2029 -
Journal of Voice : Official Journal of... Mar 2024To assess the readability of online materials related to puberphonia. (Review)
Review
OBJECTIVE
To assess the readability of online materials related to puberphonia.
STUDY DESIGN
Online material review.
METHOD
The study was conducted by performing a Google search using the specific keyword "puberphonia." Subsequently, 18 websites were selected for inclusion in the review based on predefined criteria. The selected websites underwent assessment utilizing three distinct readability metrics: Simple Measure of Gobbledygook (SMOG), Flesch Reading Ease Score (FRES), and Flesch-Kincaid Grade Level (FKGL).
RESULTS
The analysis of the selected websites revealed the following mean scores: a mean FRES of 40.2, a mean FKGL of 11.8, and a mean SMOG score of 10.9. The physician-oriented websites had a mean FRES score of 35.8, a mean FKGL score of 12.5, and a mean SMOG score of 11.4. The patient-oriented websites exhibited a mean FRES score of 44.6, a mean FKGL score of 11.3, and a mean SMOG score of 10.5.
CONCLUSION
The findings of this study indicate that the readability and understandability of online resources related to puberphonia exhibit high scores, suggesting that the materials may be challenging for patients to comprehend. Addressing and enhancing the readability of these online resources is crucial, as it has the potential to enhance patient awareness and comprehension of puberphonia, ultimately leading to more informed health care decisions and improved patient outcomes.
PubMed: 38553320
DOI: 10.1016/j.jvoice.2024.03.010