Bayesian hypothesis testing procedures have gained increased acceptance in recent years. A key advantage that Bayesian tests have over classical testing procedures is their potential to quantify information in support of true null hypotheses. Ironically, default implementations of Bayesian tests prevent the accumulation of strong evidence in favor of true null hypotheses because associated default alternative hypotheses assign a high probability to data that are most consistent with a null effect. We propose the use of "nonlocal" alternative hypotheses to resolve this paradox. The resulting class of Bayesian hypothesis tests permits more rapid accumulation of evidence in favor of both true null hypotheses and alternative hypotheses that are compatible with standardized effect sizes of most interest in psychology.
Thle effects of 10-month stay at high altitude (HA) on body composition of Indian soldiers of mix~ ethnic origins with special reference to body musculature were investigated. Body density was regrl15sed from skinfold thicknesses and girth measurements. Bone mineral was estimated from body width and stature. Muscle X-ray shadow areas at upperarm and forearm and stature were correlated with body massl and a regression equation was constructed. Analysis of data indicated that muscle mass degradqd at HA. In soldiers of group I (height: 4100 m), 1.74 kg muscle mass degraded to generate 1.31 kg water. In $oldiers of group 2 (height: 3750 m), 1.38 kg muscle mass was degraded to generate 1.04 kg water. decrease in body m~ss accounted for the loss in body fat during approach march at high altitude (HA), but during r~sidence at 5400 m, fat accounted for only 27.2 per cent of the body mass loss. These aut~ors concluded that muscle catabolism and malabsorption contributed significantly to body mass loss at HA. Rose7, f:!t al. subjected men to simulated hypoxia of Mt. Everest and observed "significant reduction in the muscle X-ray shadow areas of thigh and upperarm and a significant loss in the mean pody mass evaluated by the densitometric technique.The above studies indicate that skeletal muscle may be subjected to degradation at HA, specially when individuals make strenuous physical effort and the loss in body mass may be partly due to the loss ill mllscle mllss. Rllt these stlldies were I.:UI;llll~tCJ lJil tllc :i,uJullrll~rs U1IJ 111~lIlltuil1ers whose stay ~t HA was short. Therefore, t\le present study I.INTRODUCTIpN, Significant shifts in prot-rins from muscle-tonon-muscle fracti6n without any change in total body proteins were noted by Surksl, et al. in subjects abruptly exposed to an altitude of 4300 m fc;>r two weeks. The observed body mass loss was attributed to the loss in body fat only. Consalazio2, et al. observed negative hitrogen and water balance in their subjects after four week exposure to 4300 m. Krzywicki3, et al. ,al~o reported losses in body fat, protein, w~ter and minerals in the subjects exposed to the sa.me altitude for two weeks. Rennie4, et al. repo~ted increased excretion of proteins in the urine of native high landers with pormal creatinine clearance.lProtein'uria was also found in climbers undergoing acclimatisation. Piness reported proteinuria above 3000 m tho1!1gh this was not provoked in the strenuous and exhausting part or the trip below 3000 In. The study was carried out on 21 young and healthy male volunteers from the Indian Army. They were ofmixed ethnic origins ranging between 18-30 years. In the control stpdy carried out in plains (Delhi: height above sea level 220 m). Each soldier was given a diet which consisted of 15.7.\ MJ (3750 cal), 119 9 protein, 598 9 carbohyorate and 98 9 fat per day. On completion of this study, the soldiers were divided into two groups. Group I proceeded to HA destination !ocated at 4100 m and group 2 to a destination at 3700 m above the sea level. A...
Bayes factors represent a useful alternative to P -values for reporting outcomes of hypothesis tests by providing direct measures of the relative support that data provide to competing hypotheses. Unfortunately, the competing hypotheses have to be specified, and the calculation of Bayes factors in high-dimensional settings can be difficult. To address these problems, we define Bayes factor functions (BFFs) directly from common test statistics. BFFs depend on a single noncentrality parameter that can be expressed as a function of standardized effects, and plots of BFFs versus effect size provide informative summaries of hypothesis tests that can be easily aggregated across studies. Such summaries eliminate the need for arbitrary P -value thresholds to define “statistical significance.” Because BFFs are defined using nonlocal alternative prior densities, they provide more rapid accumulation of evidence in favor of true null hypotheses without sacrificing efficiency in supporting true alternative hypotheses. BFFs can be expressed in closed form and can be computed easily from z , t , χ 2 , and F statistics.
Skinfold thickness, body weight, body water, anthropometric measurements and segment volumes were determined in 28 young and healthy Indian soldiers on return to Delhi (200 m) after staying for more than 24 months at high altitude (3500 m). The measurements were made on the 2nd day and after 3 weeks. Ten subjects were then randomly selected from this group and returned by air to the high-altitude station, and the measurements were repeated on the 3rd and 12th day of their reinduction. Though body weight and total body water increased marginally on transfer to the lower altitude, body density remained more or less unchanged. There were significant increases in the thickness of skinfolds, even when body density had increased. During this period hand and foot volumes decreased significantly. Despite significant increases in thoracic skinfold thickness, the torso volume decreased slightly. On returning to high altitude, the soldiers lost body weight, were hypohydrated and showed reduced skinfold thickness. Fat losses calculated on the basis of reduction in skinfold thickness were far in excess of those calculated from losses in body weight and in total body water. As the reduced skinfold thickness was unrelated to changes in body water content at high altitude, it seems that such reductions are due to redistribution of blood in the skin. From the results of these investigations it is concluded that variations in skinfold thickness during acclimatisation to high altitude do not accurately represent the changes in body fat content.
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