Positive Skew Research Articles

Boundary Conditions for the Positive Skew Bias.

Gambles that involve a large but unlikely gain coupled with a small but likely loss-like a lottery ticket-are known as positively-skewed. There is evidence that people tend to prefer these positively skewed choices, leading to what is called a positive-skew bias. In this study, we attempt to better understand under what conditions people are more drawn toward positively skewed, relative to symmetric, gambles. Based on the animal literature, there is reason to believe that preference for skewed gambles is dependent on the strength of the skew, with a greater preference for more strongly skewed options. In two online studies (Study 1: N = 209; Study 2: N = 210), healthy participants across the lifespan (ages 22-85) made a series of choices between a positively skewed risky gamble and either a certain outcome (Study 1) or risky symmetric gamble (Study 2). Logistic regression analyses revealed that people were more likely to choose moderately- and strongly skewed gambles over certain outcomes, with the exception of when there were large potential losses (Study 1). However, a stronger skewness did not increase preference for positively skewed gambles over symmetric gambles, findings which also may depend on the valence of the expected outcome (Study 2). Taken together, these results suggest that there may be a greater preference for more strongly positively skewed gambles but it 1) is dependent on what other gamble is presented and 2) is most prevalent for positive expected values. Additionally, contrary to previous findings, we did not find strong evidence of an age-related increase in positive skew bias in either study. However, exploratory analyses revealed that decision making strategy and cognitive abilities may play a role.

The complete mitochondrial genome of the soil mite Cycetogamasus diviortus (Acari, Parasitidae) and the related phylogenetic analyses

Mites of the family Parasitidae Oudemans, 1901 (Acari, Mesostigmata) are widely distributed in soil and litter; some species harbor humus. In this study, we sequenced the complete mitochondrial genome of Cycetogamasus diviortus, representing a typical arthropod circular genome, with 14,450 bp in length, and encoding 37 genes. The gene order is in line with the reported mitochondrial genomes of other parasitid mite species. Except ND1 and ND5 start with TTG, other genes start with ATN. TAG is the stop codon of COX2, ND3 and ND4. COX3, CYTB and ND1 have special stop codons, which are incomplete stop codons T-, T- and A-, respectively. Other genes end in TAA. All tRNA genes show the typical cloverleaf secondary structures, except for the trnS1 (AGN), which lacks the DHU arm and is replaced by a simple loop. The whole mitochondrial genome of C. diviortus showed a heavy AT nucleotide bias (70.71%), a positive AT Skew (0.009), and a negative GC Skew (-0.267). Phylogenetic analyses were performed using Bayesian and Maximum Likelihood methods based on the dataset of mitochondrial nucleotide sequences of 22 mite species. The results showed that Parasitidae and Ologamasidae were more closely related to each other than other Mesostigmata groups.

Skewness of mean transverse momentum fluctuations in heavy-ion collisions

We propose the skewness of mean transverse momentum, $\langle p_t \rangle$, fluctuations as a fine probe of hydrodynamic behavior in relativistic nuclear collisions. We describe how the skewness of the $\langle p_t \rangle$ distribution can be analyzed experimentally, and we use hydrodynamic simulations to predict its value. We predict in particular that $\langle p_t \rangle$ fluctuations have positive skew, which is significantly larger than if particles were emitted independently. We elucidate the origin of this result by deriving generic formulas relating the fluctuations of $\langle p_t \rangle$ to the fluctuations of the early-time thermodynamic quantities. We postulate that the large positive skewness of $\langle p_t \rangle$ fluctuations is a generic prediction of hydrodynamic models.

The SKEW index: Extracting what has been left

This study disentangles a measure of implied skewness that is related to downward movements in the U.S. equity index from the corresponding implied skewness that is associated with upward movements. A positive SKEW index is constructed from S&P 500 call options, whereas a negative SKEW index is constructed from the S&P 500 put options. We show that the positive SKEW is linked to market sentiment, whereas the negative SKEW is related to existing tail risk measures. The negative SKEW is proposed as a more objective prudent tail risk measure, and it is found to be able to predict recessions, market downturns, and uncertainty indicators up to one year in advance. The predictive power of the negative SKEW is also confirmed when we control for other tail risk measures and also out-of-sample.

The SKEW Index: Extracting What Has Been Left

This study disentangles a measure of implied skewness that is related to downward movements in the U.S. equity index from the corresponding implied skewness that is associated with upward movements. A positive SKEW index is constructed from S&P500 call options, whereas a negative SKEW index is constructed from the S&P500 put options. We show that the positive SKEW is linked to market sentiment, whereas the negative SKEW is related to existing tail risk measures. The negative SKEW is proposed as a more objective prudent tail risk measure, and it is found to be able to predict recessions, market downturns, and uncertainty indicators up to one year in advance. The predictive power of the negative SKEW is also confirmed when we control for other tail risk measures and also out-of-sample.

The Phylogenetic Implications of the Mitochondrial Genomes of Macropsis notata and Oncopsis nigrofasciata.

Macropsinae are forest pests that feed on woody plants. They can damage the growth of trees and crops, and some species can also spread plant pathogens. Due to their widespread effects, these leafhoppers are of great economic significance, which is why there is a need to study their genomes. To fill the gap in the mitochondrial genomic data of the subfamily Macropsinae, we sequenced the complete mitochondrial genomes of Macropsis notata and Oncopsis nigrofasciata (which were 16,323 and 15,927 bp long, respectively). These two species are representative species of the leafhoppers group (Cicadellidae); the mitochondrial genomes of these species range from a length of 15,131 bp (Trocnadella arisana) to 16,811 bp (Parocerus laurifoliae). Both mitogenomes contained 37 typical insect mitochondrial genes and a control region; there were no long non-coding sequences. The genes within the mitogenome were very compact. The mitogenomes from both species contained two kinds of parallel repeat units in the control region. The whole mitogenomes of Macropsinae showed a heavy AT nucleotide bias (M. notata 76.8% and O. nigrofasciata 79.0%), a positive AT Skew (0.15 and 0.12), and a negative GC Skew (–0.14 and –0.08). Upon comparative ML and BI analysis, some clade relationships were consistent among the six trees. Most subfamilies were reconstructed into monophyletic groups with strong support in all analyses, with the exception of Evacanthinae and Cicadellinae. Unlike the results of previous research, it was shown that although all Deltocephalinae species are grouped into one clade, they were not the sister group to all other leafhoppers. Further, Cicadellinae and Evacanthinae were occasionally reconstructed as a polyphyletic and a paraphyletic group, respectively, possibly due to the limited numbers of samples and sequences. This mitogenome information for M. notata and O. nigrofasciata could facilitate future studies on the mitogenomic diversity and evolution of the related Membracoidea, and eventually help to control their effects on plants for the betterment of society at large.

Practical Applications of Skew and Trend Aversion: The Impact of Positive Skew and Behavioral Biases on Allocation Decisions

Practical Applications Summary In Skew and Trend Aversions: The Impact of Positive Skew and Behavioral Biases on Allocation Decisions, from the Winter 2020 issue of The Journal of Alternative Investments, Zachary Dugan (International Standard Asset Management, Johns Hopkins University) and Alexander Greyserman (International Standard Asset Management) investigate potential reasons for small portfolio allocations to trend-following strategies that are observed in most portfolios. Trend-following strategies can deliver “crisis alpha,” which is a positive return when markets are down. Their returns are positively skewed with a low correlation with the S&P 500, but their average returns are close to the S&P 500. These characteristics indicate that most portfolios could benefit from a healthy allocation to this strategy. The authors explain that investors are particularly prone to behavioral biases when evaluating strategies that have positively skewed returns. By quantifying biases implied by suboptimal portfolio allocations to trend-following strategies, they expose commonly chosen poor allocation decisions so that the reader can avoid making suboptimal choices. TOPICS:In portfolio management, risk management, wealth management, performance measurement

Skew and Trend Aversion: The Impact of Positive Skew and Behavioral Biases on Allocation Decisions

Despite overwhelming evidence of the portfolio benefits, actual investor allocations to trend following strategies are typically 5% or less. Why is there such a significant discrepancy between the optimal allocation and actual allocation to Trend? The authors investigate known behavioral biases as a potential reason. In this article, the authors explore loss aversion, recency bias, and the ambiguity effect as they pertain to trend following, and define the combination of the three trend aversion. The authors quantify trend aversion and show that these biases are a viable explanation for suboptimal allocations to Trend. The authors demonstrate a direct connection between quantifications of known behavioral biases and current suboptimal allocations to trend following. Recognition of this relationship will help allocators make better decisions and construct more robust portfolios. <b>TOPICS:</b>In portfolio management, analysis of individual factors/risk premia, risk management, wealth management, performance measurement <b>Key Findings</b> • We quantify behavioral biases and show they are a viable explanation for sub-optimal allocations to trend following. • The quantitative levels of loss aversion necessary to justify typical allocations to trend following are consistent with psychological studies. • The combination of loss aversion and recency bias is particularly impactful on trend following because of its positive skew.

Preference for luminance histogram regularities in natural scenes

Natural scene luminance distributions typically have positive skew, and for single objects, there is evidence that higher skew is a correlate (but not a guarantee) of glossiness. Skewness is also relevant to aesthetics: preference for glossy single objects (with high skew) has been shown even in infants, and skewness is a good predictor of fruit freshness. Given that primate vision appears to efficiently encode natural scene luminance variation, and given evidence that natural scene regularities may be a prerequisite for aesthetic perception in the spatial domain, here we ask whether humans in general prefer natural scenes with more positively skewed luminance distributions. If humans generally prefer images with the higher-order regularities typical of natural scenes and/or shiny objects, we would expect this to be the case. By manipulating luminance distribution skewness (holding mean and variance constant) for individual natural images, we show that in fact preference varies inversely with increasing positive skewness. This finding holds for: artistic landscape images and calibrated natural scenes; scenes with and without glossy surfaces; landscape scenes and close-up objects; and noise images with natural luminance histograms. Across conditions, humans prefer images with skew near zero over higher skew images, and they prefer skew lower than that of the unmodified scenes. These results suggest that humans prefer images with luminances that are distributed relatively evenly about the mean luminance, i.e., images with similar amounts of light and dark. We propose that our results reflect an efficient processing advantage of low-skew images over high-skew images, following evidence from prior brain imaging results.

PS-118 Discerning The Impact Of The Internship Experience For The Basic Specialist Trainee In Paediatrics (bstp)

<h3></h3> This study was designed to determine the impact of the internship experience on the BSTP. The survey evaluated job allocations, intern education, clinical skills development, and exposure to patient care. A combination of binary responses (yes, no) and Likert scoring (cuing at 1 never/disagree, and at 6 always/strongly agree) were used to code responses. Thirty five trainees responded (all those present at a study day), representing 60% of all trainees. These trainees undertook approximately 130 rotations, with 12 (34%) undertaking a paediatric rotation. Relating to intern education; only 10 (28%) of trainees had a mentor. Education was frequently provided as scheduled (Likert mean (LM) 3.82). The preferred method of teaching was bedside delivered. Interns strongly agreed that time management (LM 5.0, Positive skew (PS) 82%) and communication skills (LM 4.9, PS 71%) were clinical skills developed during intern year Relating to exposure to patient care; Interns were frequently out of their comfort zone in dealing with patients (LM 4.3, PS 41%). Most said they had never been debriefed after attending an emergency situation (LM 1.7, PS 3%). An elevated Early Warning Score (EWS) in Irish hospitals precludes intern assessment however this rule is frequently ignored (LM 4.9, PS 80%). Interns infrequently clerked patients in the emergency department (LM 2.6, PS 14%), although many agreed that interns should be clerking patients (LM 4.4, PS 55%) This survey highlights the variability of the internship experience in Ireland, and highlights some areas where direct improvements could be made.

ANALYSIS OF AN OPTION MARKET DYNAMICS BASED ON A HETEROGENEOUS AGENT MODEL

We propose a two-market model in which an option market and its underlying market interact. Many artificial markets representing stock markets have been developed, and these models have been actively used to investigate the effects of market rules. However, no artificial market model for derivatives has been intensively studied, even though derivative markets are increasingly important. We tested stylized facts that can be observed in an option market and our model can replicate fat-tailed distributions, positive skew of the return and positive autocorrelation of the square of return of implied volatility. We found that the speed of volatility mean reversion for fundamentalists and the existence of chartists are important factors for replicating the positive skew of an option market. The value of fat-tailed distributions and positive skewness of the return get closer to the real value by coupling an option market and an underlying market. Copyright © 2014 John Wiley & Sons, Ltd.

Effect of temporal autocorrelation on apparent growth rate variation in forest tree census data and an alternative distribution function of tree growth rate

AbstractDistributions of forest tree growth rates often display wide variation and positive skewness even within a narrow range of tree sizes. Temporal autocorrelation of growth rates is also commonly observed in forest trees. We suggest that temporal autocorrelation causes the positive skew in growth rate distributions. We propose the ‘passage’ distribution of growth rates, defined by the density of trees passing a particular size over a given inter‐census interval, as a superior description of growth performance of trees with temporally autocorrelated growth. We relate the passage distribution to the conventional ‘resident’ distribution of growth rates, defined by the growth rates of trees within a particular size range at a given census. The passage distribution is approximated by the resident distribution weighted by the absolute growth rate. For common rain forest tree populations, the average of the passage distribution is nearly twice that of the resident distribution. Simulation models which use growth rates estimated from resident distributions and assume a Markov process are valid only to reconstruct the dynamics of the overall size structure of a stand. When examining the influence of life history strategy on forest dynamics, models must incorporate the effect of temporal autocorrelation on growth rates.

Technological inefficiency and the skewness of the error component in stochastic frontier analysis

This paper concentrates on negatively skewed one-sided distributions as an explanation of the occurrence of positive (negative) skewness in the case of stochastic production (cost) frontier analysis. It takes as an example the binomial distribution that can have negative or positive skew and derives the method-of-moments estimators.

Skewness, sampling risk, and the importance of diversification

Recent papers have extended portfolio theory to include skewness along with mean return and variance to explain security preferences. Because the positive skewness typically present in individual assets such as stocks and call options is rapidly reduced through diversification, several authors have suggested that a preference for positive skewness can lead to antidiversification as investors attempt to capture the greatest amount of positive skew. These analyses ignore the sampling risk (the probability that the skewness of a particular portfolio of size n will be near its expected value) that exists when less than fully diversified portfolios are held. This analysis presents skewness statistics for three security populations over three market periods to illustrate the relationship between sampling risk and diversification. Small portfolios of stocks or call options are shown to possess greater expected skewness than larger portfolios for each sample period examined, but small portfolios also exhibit the greatest sampling risk for skewness. Depending upon an investor's skewness preference, some diversification in these assets appears appropriate to increase the confidence regarding the actual skewness that will be observed for a particular portfolio chosen. Expected skewness for covered call portfolios is negative for all portfolio sizes and sample periods and declines as portfolio size inreases. The elimination of sampling risk and the reduction of negative expected skewness can be accomplished through complete diversification in these assets.

How does flow cytometry express Gaussian distributed biological information?

The analogue-to-digital conversion step in flow cytometric analysis introduces a positive skew into the distribution of any measured parameter. In this communication we describe a semi-analytical method to determine if a distribution skewed by the analogue-to-digital conversion step is compatible with a Gaussian origin. The procedure involves determining the errors associated with calculating the coefficient of variation from the skewed distribution and applying systematic corrections. The method was tested with a number of experimental data sets and is illustrated with 3 distributions. One of these was not compatible with a Gaussian origin, but the other 2 were, in spite of considerable positive skewness in the data.

Variations in growth and reproduction within populations of two rhizomatous plant species: Typha latifolia and Typha angustifolia.

Seasonal excavations of ramet systems in overlapping natural populations of Typha latifolia and T. angustifolia revealed intrapopulation variation in ramet size and reproduction. Reproductive "states" were recognized based on whether or not a ramet had flowered and the number of offspring ramets it possessed. As the growing season progressed, the populations became increasingly heterogeneous in their reproductive-state composition with the largest size classes of ramets containing the greatest number of reproductive states. Therefore, despite a strong correlation between size and reproduction, average ramet size was considered to be an inadequate predictor of population growth in ramet numbers. Results for vegetative reproduction and ramet mortality indicate that the T. latifolia population was growing while the T. angustifolia population was approximately stable. In contrast to most results reported for other species, the frequency distributions of ramet size classes showed T. angustifolia to have a normally distributed population. A slight degree of positive skewing occurred in T. latifolia with the greatest skewing at the end of the growing season. Despite the lack of strong skewing of ramet weights, evidence from other sources have demonstrated that competition was intense and we hypothesize that competition in clonal populations may not not always act to cause positive skew in weight distributions.