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Ecology and Evolution Nov 2022Many primary research studies in ecology are underpowered, providing very imprecise estimates of effect size. Meta-analyses partially mitigate this imprecision by...
Many primary research studies in ecology are underpowered, providing very imprecise estimates of effect size. Meta-analyses partially mitigate this imprecision by combining data from different studies. But meta-analytic estimates of mean effect size may still remain imprecise, particularly if the meta-analysis includes a small number of studies. Imprecise, large-magnitude estimates of mean effect size from small meta-analyses likely would shrink if additional studies were conducted (regression towards the mean). Here, I propose a way to estimate and correct this regression to the mean, using meta-meta-analysis (meta-analysis of meta-analyses). Hierarchical random effects meta-meta-analysis shrinks estimated mean effect sizes from different meta-analyses towards the grand mean, bringing those estimated means closer on average to their unknown true values. The intuition is that, if a meta-analysis reports a mean effect size much larger in magnitude than that reported by other meta-analyses, that large mean effect size likely is an overestimate. This intuition holds even if different meta-analyses of different topics have different true mean effect sizes. Drawing on a compilation of data from hundreds of ecological meta-analyses, I find that the typical (median) ecological meta-analysis overestimates the absolute magnitude of the true mean effect size by ~10%. Some small ecological meta-analyses overestimate the magnitude of the true mean effect size by >50%. Meta-meta-analysis is a promising tool for improving the accuracy of meta-analytic estimates of mean effect size, particularly estimates based on just a few studies.
PubMed: 36407900
DOI: 10.1002/ece3.9521 -
European Journal of Radiology Feb 2022This study aimed to clarify the relationship between the severity of the calcium burden in the most calcified coronary vessel and coronary artery disease (CAD).
PURPOSE
This study aimed to clarify the relationship between the severity of the calcium burden in the most calcified coronary vessel and coronary artery disease (CAD).
METHOD
Of 2150 patients, 376 examined by both coronary computed tomographic angiography and invasive coronary angiography (ICA) within 30 days at Sun Yat-sen Memorial Hospital between March 2011 and July 2020 were included. Three coronary artery calcium scores (CACSs), including the Agatston score, volume score, and mass score, and other clinical variables were recorded. The ratio of max-to-mean CACS in the most calcified vessel (CACS) was defined as the CACS in the most calcified vessel/average CACS of the four major epicardial coronary arteries. Logistic regression and least absolute shrinkage and selection operator (LASSO) analyses were performed to assess the relationship between CACS and CAD.
RESULTS
CACS was higher in 81.1% of subjects diagnosed with CAD than in subjects without CAD. In multivariate logistic regression analysis, CACS determined by the Agatston score, volumetric score, and mass score was associated with CAD. In LASSO analysis, Agatston score (not the total Agatston score or other CACS) had the strongest correlation with CAD (β = 0.125). AUCs in the training set and the validation set were 0.811 and 0.789, respectively. Increased age, diabetes and hypertension correlated with higher Agatston score.
CONCLUSIONS
In addition to total CACS, CACS may be a novel diagnostic parameter for CAD, showing the calcium burden severity.
Topics: Calcium; Computed Tomography Angiography; Coronary Angiography; Coronary Artery Disease; Humans; Predictive Value of Tests
PubMed: 34979296
DOI: 10.1016/j.ejrad.2021.110134 -
Turkish Journal of Medical Sciences Feb 2016Activation and size of platelets have been suggested to be involved in the pathogenesis of vascular complications in diabetes mellitus. The purpose of the present study...
BACKGROUND/AIM
Activation and size of platelets have been suggested to be involved in the pathogenesis of vascular complications in diabetes mellitus. The purpose of the present study was to investigate the association of mean platelet volume with microalbuminuria in type 2 diabetic patients.
MATERIALS AND METHODS
Mean platelet volume levels were investigated in healthy participants and type 2 diabetic patients with and without microalbuminuria. After their mean platelet volume values were compared, correlation of mean platelet volume with sex, duration of diabetes, microalbuminuria, fasting blood glucose, hemoglobin A1c, creatinine clearance, and body mass index was examined.
RESULTS
Mean platelet volume levels were higher in all diabetic patients than those in controls. Mean platelet volume levels were highest in diabetics with microalbuminuria. The mean platelet volume levels had a positive correlation with microalbuminuria.
CONCLUSION
Mean platelet volume values of diabetic patients were higher than those of nondiabetics, the highest levels being in diabetics with microalbuminuria. Our results suggest that microalbuminuria might be related with mean platelet volume in diabetic patients.
Topics: Albuminuria; Blood Platelets; Diabetes Mellitus, Type 2; Glycated Hemoglobin; Humans; Mean Platelet Volume
PubMed: 27511481
DOI: 10.3906/sag-1410-94 -
The Journal of the Acoustical Society... Jul 2022Spectral properties of earlier sounds (context) influence recognition of later sounds (target). Acoustic variability in context stimuli can disrupt this process. When...
Spectral properties of earlier sounds (context) influence recognition of later sounds (target). Acoustic variability in context stimuli can disrupt this process. When mean fundamental frequencies (f0's) of preceding context sentences were highly variable across trials, shifts in target vowel categorization [due to spectral contrast effects (SCEs)] were smaller than when sentence mean f0's were less variable; when sentences were rearranged to exhibit high or low variability in mean first formant frequencies (F) in a given block, SCE magnitudes were equivalent [Assgari, Theodore, and Stilp (2019) J. Acoust. Soc. Am. 145(3), 1443-1454]. However, since sentences were originally chosen based on variability in mean f0, stimuli underrepresented the extent to which mean F could vary. Here, target vowels (/ɪ/-/ɛ/) were categorized following context sentences that varied substantially in mean F (experiment 1) or mean F (experiment 2) with variability in mean f0 held constant. In experiment 1, SCE magnitudes were equivalent whether context sentences had high or low variability in mean F; the same pattern was observed in experiment 2 for new sentences with high or low variability in mean F. Variability in some acoustic properties (mean f0) can be more perceptually consequential than others (mean F, mean F), but these results may be task-dependent.
Topics: Phonetics; Sound; Sound Spectrography; Speech Acoustics; Speech Perception
PubMed: 35931547
DOI: 10.1121/10.0011920 -
Computer Methods and Programs in... Sep 2021Eyestrain has been increasingly severe in our lives and works as the progress of computers and smartphones. Evaluating eyestrain helps to prevent and relieve eyestrain....
BACKGROUND AND OBJECTIVE
Eyestrain has been increasingly severe in our lives and works as the progress of computers and smartphones. Evaluating eyestrain helps to prevent and relieve eyestrain. Our study aimed to evaluate eyestrain by analyzing vertical electrooculogram (VEOG).
METHODS
21 young subjects were asked to watch a video on the computer for a totally 120 minutes each, during which the VEOG signal was acquired using only three electrodes, and the questionnaire was answered every 30 minutes. The VEOG signal was divided into four 30-minute phases, from which VEOG signal power probability (VEOGSPP) features and blink features were extracted. The blink features include the changes of blink number (BN), group blinks number (GBN) and ratio (GBR), mean blink amplitude (Mean_BA) and duration (Mean_BD), mean blink duration at 50% (Mean_BD50), mean closing duration (Mean_CD) and opening duration (Mean_OD), mean opening duration at early 50% (Mean_ODE50) and late 50% (Mean_ODL50), mean blink maximum rising slope (Mean_BMRS) and falling slope (Mean_BMFS).
RESULTS
The results showed that the VEOGSPP in the high-frequency band (0.8-6.3Hz), BN, GBN, and GBR significantly increased while the VEOGSPP in the low-frequency band (0.1-0.4Hz), Mean_BA, Mean_OD, and Mean_ODL50 significantly decreased with eyestrain (P<0.05).
CONCLUSIONS
In conclusion, eyestrain induced by watching videos for a long time could be well evaluated by analyzing the VEOG signal.
Topics: Asthenopia; Blinking; Computers; Electrooculography; Humans; Smartphone
PubMed: 34102561
DOI: 10.1016/j.cmpb.2021.106171 -
Giornale Italiano Di Cardiologia Apr 1998Several approaches have been used for noninvasive estimation of right atrial pressure (RAP), but, no currently available method has gained any definite validation. The... (Clinical Trial)
Clinical Trial
BACKGROUND
Several approaches have been used for noninvasive estimation of right atrial pressure (RAP), but, no currently available method has gained any definite validation. The purpose of this study was to evaluate the accuracy of two-dimensional and Doppler echocardiography in estimating mean RAP in patients with cardiac disease.
METHODS
We examined the relation of mean RAP to right atrial size and function, size and respiratory changes of inferior vena cava and Doppler parameters of tricuspid and hepatic vein flow in 114 consecutive patients (77 men, 37 women; mean age 57 +/- 12 years) with various cardiac diseases undergoing cardiac catheterization. Echocardiographic studies were performed within 24 hours before catheterization (mean interval 6 +/- 3 hours). Patients were assigned to 3 groups according to the values of mean RAP (group 1, < or = 8 mmHg; group 2, between 9 and 12 mmHg; group 3, > 12 mmHg).
RESULTS
Mean RAP ranged from 3 to 20 mmHg (mean 9.1 +/- 4.3 mmHg). It correlated most strongly with the collapsibility index of inferior vena cava (IVCCI) (r = -0.76), minimal inspiratory diameter of inferior vena cava (r = 0.72) and deceleration time of early tricuspid flow (DT) (r = -0.61). Discriminant analysis demonstrated that IVCCI and DT were major determinants of mean RAP with 81.6% of cases correctly assigned to study groups: 96% of patients of group 1 and 87% of patients of group 3 were identified, whereas the accuracy in identifying the patients of group 2 was lower (46%). An IVCCI > 45% was the best cutoff point in predicting a mean RAP < or = 8 mmHg; an IVCCI < 35% and a DT < 150 msec were the best cutoff points in predicting a mean RAP > or = 15 mmHg. The best multivariate equation predicting mean RAP was: mean RAP = 23.3 - 0.2 IVCCI -0.026 DT (r = 0.80, R2 = 0.64). This equation was 81% sensitive and 84% specific in detecting a mean RAP < or = 8 mmHg and 74% sensitive and 97% specific in detecting a mean RAP > 12 mmHg.
CONCLUSIONS
Mean RAP can be estimated noninvasively by two-dimensional and Doppler echocardiography. The combined analysis of IVCCI and DT provides an accurate prediction on mean RAP < or = 8 mmHg and > 12 mmHg, whereas the prediction of intermediate values is less accurate.
Topics: Adult; Aged; Aged, 80 and over; Atrial Function, Right; Blood Pressure; Cardiac Catheterization; Echocardiography; Echocardiography, Doppler; Female; Heart Diseases; Humans; Male; Middle Aged; Reproducibility of Results
PubMed: 9616849
DOI: No ID Found -
Canadian Journal of Psychiatry. Revue... Nov 2000There are many indices of the middle, or central tendency, of a set of numbers, including the mode, median, and mean. Indeed, there are, several "means," of which the...
There are many indices of the middle, or central tendency, of a set of numbers, including the mode, median, and mean. Indeed, there are, several "means," of which the arithmetic mean is only one. When data are skewed, or when there are outliers at one or both ends of the distribution that may distort the results, "robust" estimators of the mean, such as the trimmed mean or the bisquare weight mean, give better results than does the arithmetic mean. If the data reflect growth over time, the geometric mean is a more accurate reflection of the middle point than are other indices, and in determining sample size when the sample size varies among groups, the harmonic mean is the one of choice. Finally, this paper discusses the difference between the lay and statistical use of the term "average" and how this difference can lead to problems in interpretation.
Topics: Data Interpretation, Statistical; Humans; Psychiatry; Psychometrics; Research Design
PubMed: 11143834
DOI: 10.1177/070674370004500908 -
Thrombosis Research Mar 2014
Topics: Adult; Asian People; Female; Humans; Male; Mean Platelet Volume; Platelet Count; Reference Values; Retrospective Studies
PubMed: 24388570
DOI: 10.1016/j.thromres.2013.12.011 -
Indian Journal of Psychological Medicine Jul 2020Many authors are unsure of whether to present the mean along with the standard deviation (SD) or along with the standard error of the mean (SEM). The SD is a descriptive...
Many authors are unsure of whether to present the mean along with the standard deviation (SD) or along with the standard error of the mean (SEM). The SD is a descriptive statistic that estimates the scatter of values around the sample mean; hence, the SD describes the sample. In contrast, the SEM is an estimate of how close the sample mean is to the population mean; it is an intermediate term in the calculation of the 95% confidence interval around the mean, and (where applicable) statistical significance; the SEM does not describe the sample. Therefore, the mean should always be accompanied by the SD when describing the sample. There are many reasons why the SEM continues to be reported, and it is argued that none of these is justifiable. In fact, presentation of SEMs may mislead readers into believing that the sample data are more precise than they actually are. Given that the standard error is not presented for other parameters, such as difference between means or proportions, and difference between proportions, it is suggested that presentation of SEM values can be done away with, altogether.
PubMed: 33402813
DOI: 10.1177/0253717620933419 -
Journal of Applied Physiology... Aug 1986Mean airway pressure underestimates mean alveolar pressure during high-frequency oscillatory ventilation. We hypothesized that high inspiratory flows characteristic of...
Mean airway pressure underestimates mean alveolar pressure during high-frequency oscillatory ventilation. We hypothesized that high inspiratory flows characteristic of high-frequency jet ventilation may generate greater inspiratory than expiratory pressure losses in the airways, thereby causing mean airway pressure to overestimate, rather than underestimate, mean alveolar pressure. To test this hypothesis, we ventilated anesthetized paralyzed rabbits with a jet ventilator at frequencies of 5, 10, and 15 Hz, constant inspiratory-to-expiratory time ratio of 0.5 and mean airway pressures of 5 and 10 cmH2O. We measured mean total airway pressure in the trachea with a modified Pitot probe, and we estimated mean alveolar pressure as the mean pressure corresponding in the static pressure-volume relationship to the mean volume of the respiratory system measured with a jacket plethysmograph. We found that mean airway pressure was similar to mean alveolar pressure at frequencies of 5 and 10 Hz but overestimated it by 1.1 and 1.4 cmH2O at mean airway pressures of 5 and 10 cmH2O, respectively, when frequency was increased to 15 Hz. We attribute this finding primarily to the combined effect of nonlinear pressure frictional losses in the airways and higher inspiratory than expiratory flows. Despite the nonlinearity of the pressure-flow relationship, inspiratory and expiratory net pressure losses decreased with respect to mean inspiratory and expiratory flows at the higher rates, suggesting rate dependence of flow distribution. Redistribution of tidal volume to a shunt airway compliance is thought to occur at high frequencies.(ABSTRACT TRUNCATED AT 250 WORDS)
Topics: Animals; Mathematics; Physiology; Plethysmography; Pressure; Pulmonary Alveoli; Rabbits; Respiration, Artificial; Trachea
PubMed: 3745038
DOI: 10.1152/jappl.1986.61.2.456