SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Variance

351

Using mixed design analysis of variance (ANOVA), this paper investigates the effects of a subtle simulated increase in adiposity on women’s employment chances in the service sector. Employing a unique simulation of altering individuals' BMIs and the literature on “aesthetic labour”, the study suggests that, especially for women, being heavier, but still within a healthy BMI, deleteriously impacts on hireability ratings. The paper explores the gendered dimension of this prejudice by asking whether female employees at the upper end of a healthy BMI range are likely to be viewed more negatively than their overtly overweight male counterparts. The paper concludes by considering the implications of these findings.

Concepts: Male, Female, Variance, Gender, Normal distribution, Woman, Analysis of variance, Chi-square distribution

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BACKGROUND: Slow eating has been associated with enhanced satiation, but also with increased water intake. Therefore, the role of water ingestion in regard to eating rate needs to be discerned. This study examined the influence of eating rate on appetite regulation and energy intake when water intake is controlled. METHODS: In a randomized design, slow and fast eating rates were compared on two occasions, in 30 women (22.7+/-1.2y; BMI=22.4+/-0.4kg/m2) who consumed an ad libitum mixed-macronutrient lunch with water (300 mL). Satiation was examined as the main outcome by measuring energy intake during meals. At designated times, subjects rated hunger, satiety, desire-to-eat, thirst, and meal palatability on visual analogue scales. Paired t-tests were used to compare hypothesis-driven outcomes. Appetite ratings were compared across time points and conditions by repeated measures analysis of variance (ANOVA) using a within-subject model. RESULTS: Energy intake and appetite ratings did not differ between conditions at meal completion. However, subjects rated less hunger and tended to rate lower desire-to-eat and greater satiety at 1 hour following the slow condition. CONCLUSIONS: Results tend to support a role of slow eating on decreased hunger and higher inter-meal satiety when water intake is controlled. However, the lack of significant differences in energy intake under these conditions indicates that water intake may account for the effects of eating rate on appetite regulation.

Concepts: Nutrition, Variance, Water, Eating, Normal distribution, Analysis of variance, Appetite, Food and drink

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BACKGROUND: Lidar height data collected by the Geosciences Laser Altimeter System (GLAS) from 2002 to 2008 has the potential to form the basis of a globally consistent sample-based inventory of forest biomass. GLAS lidar return data were collected globally in spatially discrete full waveform “shots,” which have been shown to be strongly correlated with aboveground forest biomass. Relationships observed at spatially coincident field plots may be used to model biomass at all GLAS shots, and well-established methods of model-based inference may then be used to estimate biomass and variance for specific spatial domains. However, the spatial pattern of GLAS acquisition is neither random across the surface of the earth nor is it identifiable with any particular systematic design. Undefined sample properties therefore hinder the use of GLAS in global forest sampling. RESULTS: We propose a method of identifying a subset of the GLAS data which can justifiably be treated as a simple random sample in model-based biomass estimation. The relatively uniform spatial distribution and locally arbitrary positioning of the resulting sample is similar to the design used by the US national forest inventory (NFI). We demonstrated model-based estimation using a sample of GLAS data in the US state of California, where our estimate of biomass (211 Mg/hectare) was within the 1.4% standard error of the design-based estimate supplied by the US NFI. The standard error of the GLAS-based estimate was significantly higher than the NFI estimate, although the cost of the GLAS estimate (excluding costs for the satellite itself) was almost nothing, compared to at least US$ 10.5 million for the NFI estimate. CONCLUSIONS: Global application of model-based estimation using GLAS, while demanding significant consolidation of training data, would improve inter-comparability of international biomass estimates by imposing consistent methods and a globally coherent sample frame. The methods presented here constitute a globally extensible approach for generating a simple random sample from the global GLAS dataset, enabling its use in forest inventory activities.

Concepts: Statistics, Variance, Mathematics, Simple random sample, Sample size, Estimation theory, Estimator, Sampling

30

Classic evolutionary and social exchange perspectives suggest that some people have more mate value than others because they possess desirable traits (e.g., attractiveness, status) that are intrinsic to the individual. This article broadens mate value in 2 ways to incorporate relational perspectives. First, close relationships research suggests an alternative measure of mate value: whether someone can provide a high quality relationship. Second, person perception research suggests that both trait-based and relationship quality measures of mate value should contain a mixture of target variance (i.e., consensus about targets, the classic conceptualization) and relationship variance (i.e., unique ratings of targets). In Study 1, participants described their personal conceptions of mate value and revealed themes consistent with classic and relational approaches. Study 2 used a social relations model blocked design to assess target and relationship variances in participants' romantic evaluations of opposite-sex classmates at the beginning and end of the semester. In Study 3, a one-with-many design documented target and relationship variances among long-term opposite-sex acquaintances. Results generally revealed more relationship variance than target variance; participants' romantic evaluations were more likely to be unique to a particular person rather than consensual. Furthermore, the relative dominance of relationship to target variance was stronger for relational measures of mate value (i.e., relationship quality projections) than classic trait-based measures (i.e., attractiveness, resources). Finally, consensus decreased as participants got to know one another better, and long-term acquaintances in Study 3 revealed enormous amounts of relationship variance. Implications for the evolutionary, close relationships, and person-perception literatures are discussed. (PsycINFO Database Record © 2014 APA, all rights reserved).

Concepts: Relationship, Variance, Evaluation, Sociology, Interpersonal relationship, All rights reserved, Target Corporation, Uniqueness quantification

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Ferley, DD, Osborn, RW, and Vukovich, MD. The effects of uphill vs. level-grade high-intensity interval training on V[Combining Dot Above]O2max, Vmax, VLT, and Tmax in well-trained distance runners. J Strength Cond Res 27(6): 1549-1559, 2013-Uphill running represents a frequently used and often prescribed training tactic in the development of competitive distance runners but remains largely uninvestigated and unsubstantiated as a training modality. The purpose of this investigation included documenting the effects of uphill interval training compared with level-grade interval training on maximal oxygen consumption (V[Combining Dot Above]O2max), the running speed associated with V[Combining Dot Above]O2max (Vmax), the running speed associated with lactate threshold (VLT), and the duration for which Vmax can be sustained (Tmax) in well-trained distance runners. Thirty-two well-trained distance runners (age, 27.4 ± 3.8 years; body mass, 64.8 ± 8.9 kg; height, 173.6 ± 6.4 cm; and V[Combining Dot Above]O2max, 60.9 ± 8.5 ml·min·kg) received assignment to an uphill interval training group (GHill = 12), level-grade interval training group (GFlat = 12), or control group (GCon = 8). GHill and GFlat completed 12 interval and 12 continuous running sessions over 6 weeks, whereas GCon maintained their normal training routine. Pre- and posttest measures of V[Combining Dot Above]O2max, Vmax, VLT, and Tmax were used to assess performance. A 3 × 2 repeated measures analysis of variance was performed for each dependent variable and revealed a significant difference in Tmax in both GHill and GFlat (p < 0.05). With regard to running performance, the results indicate that both uphill and level-grade interval training can induce significant improvements in a run-to-exhaustion test in well-trained runners at the speed associated with V[Combining Dot Above]O2max but that traditional level-grade training produces greater gains.

Concepts: Variance, Analysis of variance, High-intensity interval training, Running, VO2 max, Interval training, Excess post-exercise oxygen consumption, Long slow distance

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Ryan, EJ, Kim, C-H, Fickes, EJ, Williamson, M, Muller, MD, Barkley, JE, Gunstad, J, and Glickman, EL. Caffeine gum and cycling performance: A timing study. J Strength Cond Res 27(1): 259-264, 2013-The purpose of this study was to determine the most efficacious time to administer caffeine (CAF) in chewing gum to enhance cycling performance. Eight male cyclists participated in 5 separate laboratory sessions. During the first visit, the subjects underwent a graded exercise test to determine maximal oxygen consumption (V[Combining Dot Above]O2max). During the next 4 visits, 3 pieces of chewing gum were administered at 3 time points (120-minute precycling, 60-minute precycling, and 5-minute precycling). In 3 of the 4 visits, at 1 of the time points mentioned previously, 300 mg of CAF was administered. During the fourth visit, placebo gum was administered at all 3 time points. The experimental trials were defined as follows: trial A (-120), trial B (-60), trial C (-5), and trial D (Placebo). After baseline measurements, time allotted for gum administration, and a standard warm-up, the participants cycled at 75% V[Combining Dot Above]O2max for 15 minutes then completed a 7-kJ·kg cycling time trial. Data were analyzed using a repeated measures analysis of variance. Cycling performance was improved in trial C (-5), but not in trial A (-120) or trial B (-60), relative to trial D (Placebo). CAF administered in chewing gum enhanced cycling performance when administered immediately prior, but not when administered 1 or 2 hours before cycling.

Concepts: Variance, Physical exercise, Exercise, Analysis of variance, VO2 max, Physical fitness, Chewing gum, Individual time trial

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STUDY DESIGN.: Prospective radiographical analysis of cranial center of mass (CCOM), C2, and C7 plumb lines in young and elderly asymptomatic individuals. OBJECTIVE.: To establish a normal range for craniosagittal balance for both young and elderly asymptomatic individuals. SUMMARY OF BACKGROUND DATA.: Global sagittal balance must account for the position of the head in relation to the spine and pelvis. The C7 plumb line defines thoracolumbar sagittal balance and has been shown to have significant impact on patient outcomes. However, the C7 plumb line fails to take into consideration the position of the head in relation to the pelvis. METHODS.: A total of 100 asymptomatic 20- to 40-year-old patients and 100 asymptomatic 60- to 80-year-old patients were enrolled. Standing plain radiographs of 14 × 36 in were obtained. CCOM, C2, and C7 plumb lines were drawn and measured from the superoposterior endplate of S1. RESULTS.: A total of 78 asymptomatic 20- to 40-year-old patients and 62 asymptomatic 60- to 80-year-old patients had adequate radiographs. The mean plumb line values in the 20- to 40-year-old patients and 60- to 80-year-old patients, respectively, were as follows; CCOM 9.0 mm (SD, 31.5 mm) and 41.2 mm (SD, 35.7 mm); C2 -2.7 mm (SD, 32.7 mm) and 32.1 mm (SD, 33.6 mm); and C7 -16.4 mm (SD, 31.5 mm) and 10.6 mm (SD, 27.8 mm). One-way analysis of variance and Student t tests confirmed that these mean plumb line values were significantly different between young and elderly patients (P < 0.001). The change at each level over time was highly correlated with the other levels (r > 0.97; P < 0.001) as did the degree of change between groups (r > 0.90, P < 0.001). CONCLUSION.: Spinopelvic alignment in conjunction with CCOM has increased our understanding of spinal balance by including the head and may better represent true global spinal balance. CCOM is an easily measured parameter by using the nasion-inion technique.

Concepts: Variance, Mass, Arithmetic mean, Normal distribution, Lead, Analysis of variance, Normative, Plumb-bob

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Members of the order Carnivora display a broad range of locomotor habits, including cursorial, scansorial, arboreal, semiaquatic, aquatic, and semifossorial species from multiple families. Ecomorphological analyses from osteological measurements have been used successfully in prior studies of carnivorans and rodents to accurately infer the locomotor habits of extinct species. This study uses 20 postcranial measurements that have been shown to be effective indicators of locomotor habits in rodents and incorporates an extensive sample of over 300 individuals from more than 100 living carnivoran species. We performed statistical analyses, including analysis of variance (ANOVA) and stepwise discriminant function analysis, using a set of 16 functional indices (ratios). Our ANOVA results reveal consistent differences in postcranial skeletal morphology among locomotor groups. Cursorial species display distal elongation of the limbs, gracile limb elements, and relatively narrow humeral and femoral epicondyles. Aquatic and semiaquatic species display relatively robust, shortened femora and elongate metatarsals. Semifossorial species display relatively short, robust limbs with enlarged muscular attachment sites and elongate claws. Both semiaquatic and semifossorial species have relatively elongate olecranon process of the ulna and enlarged humeral and femoral epicondyles. Terrestrial, scansorial, and arboreal species are characterized by having primarily intermediate features, but arboreal species do show relatively elongate manual digits. Morphological indices effectively discriminate locomotor groups, with cursorial and arboreal species more accurately classified than terrestrial, scansorial, or semiaquatic species. Both within and between families, species with similar locomotor habits converge toward similar postcranial morphology despite their independent evolutionary histories. The discriminant analysis worked particularly well to correctly classify members of the Canidae, but not as well for members of the Mustelidae or Ursidae. Results are used to infer the locomotor habits of extinct carnivorans, including members of several extinct families, and also 12 species from the Pleistocene of Rancho La Brea. J. Morphol., 2013. © 2012 Wiley Periodicals, Inc.

Concepts: Evolution, Statistics, Variance, Ulna, Mammal, Analysis of variance, Carnivora, Olecranon fossa

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The optimum sequence parameters of diffusion spectrum MRI (DSI) on clinical scanners were investigated previously. However, the scan time of approximately 30min is still too long for patient studies. Additionally, relatively large sampling interval in the diffusion-encoding space may cause aliasing artifact in the probability density function when Fourier transform is undertaken, leading to estimation error in fiber orientations. Therefore, this study proposed a non-Cartesian sampling scheme, body-centered-cubic (BCC), to avoid the aliasing artifact as compared to the conventional Cartesian grid sampling scheme (GRID). Furthermore, the accuracy of DSI with the use of half-sphere sampling schemes, i.e. GRID102 and BCC91, was investigated by comparing to their full-sphere sampling schemes, GRID203 and BCC181, respectively. In results, smaller deviation angle and lower angular dispersion were obtained by using the BCC sampling scheme. The half-sphere sampling schemes yielded angular precision and accuracy comparable to the full-sphere sampling schemes. The optimum b(max) was approximately 4750s/mm(2) for GRID and 4500s/mm(2) for BCC. In conclusion, the BCC sampling scheme could be implemented as a useful alternative to the GRID sampling scheme. Combination of BCC and half-sphere sampling schemes, that is BCC91, may potentially reduce the scan time of DSI from 30min to approximately 14min while maintaining its precision and accuracy.

Concepts: Variance, Fundamental physics concepts, Probability theory, Normal distribution, Accuracy and precision, Probability density function, Random variable, Dirac delta function

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Abstract Objective: To evaluate the impact of the incisor position on the self-perceived psychosocial impacts of malocclusion among Chinese young adults. Materials and Methods: This cross-sectional study included a convenience sample of 17.1- to 22.3-year-old young adults (n  =  1005). The five groups represented were normal occlusion as well as incisor Class I, Class II/1, Class II/2, and Class III malocclusion. For clinical assessment, the incisor relationship was evaluated according to the British Standards Institute Incisor Classification, and the self-perception of dental esthetics was assessed using the Psychosocial Impact of Dental Aesthetics Questionnaire (PIDAQ). Statistical analysis involved the analysis of variance and Tukey multiple-comparison post hoc tests. Results: Psychosocial impacts were different among the five groups for the four PIDAQ domains (P < .001 for all four domains). Statistically significant differences were found between the four malocclusion groups and the normal occlusion group in all four domains (P < .001 for all four domains). Furthermore, statistically significant differences were found between four malocclusion groups. Conclusions: All four malocclusion groups had more severe psychosocial impacts than the normal occlusion group in the four PIDAQ domains. Statistically significant differences were also found between the four malocclusion groups; these malocclusion groups ranked by score, highest to lowest, were Class III, Class II/1, Class II/2, and Class I.

Concepts: Statistics, Variance, Statistical significance, Ronald Fisher, Normal distribution, Standard deviation, Analysis of variance, Class III railroad