Effect Of Rarity Research Articles

The effects of class rarity on the evaluation of supervised healthcare fraud detection models

The United States healthcare system produces an enormous volume of data with a vast number of financial transactions generated by physicians administering healthcare services. This makes healthcare fraud difficult to detect, especially when there are considerably less fraudulent transactions (documented and readily available) than non-fraudulent. The ability to successfully detect fraudulent activities in healthcare, given such discrepancies, can garner up to $350 billion in recovered monetary losses. In machine learning, when one class has a substantially larger number of instances (majority) compared to the other (minority), this is known as class imbalance. In this paper, we focus specifically on Medicare, utilizing three ‘Big Data’ Medicare claims datasets with real-world fraudulent physicians. We create a training and test dataset for all three Medicare parts, both separately and combined, to assess fraud detection performance. To emulate class rarity, which indicates particularly severe levels of class imbalance, we generate additional datasets, by removing fraud instances, to determine the effects of rarity on fraud detection performance. Before a machine learning model can be distributed for real-world use, a performance evaluation is necessary to determine the best configuration (e.g. learner, class sampling ratio) and whether the associated error rates are low, indicating good detection rates. With our research, we demonstrate the effects of severe class imbalance and rarity using a training and testing (Train_Test) evaluation method via a hold-out set, and provide our recommendations based on the supervised machine learning results. Additionally, we repeat the same experiments using Cross-Validation, and determine it is a viable substitute for Medicare fraud detection. For machine learning with the severe class imbalance datasets, we found that, as expected, fraud detection performance decreased as the fraudulent instances became more rare. We apply Random Undersampling to both Train_Test and Cross-Validation, for all original and generated datasets, in order to assess potential improvements in fraud detection by reducing the adverse effects of class imbalance and rarity. Overall, our results indicate that the Train_Test method significantly outperforms Cross-Validation.

Under Interruptive Effects of Rarity and Mental Accounting, Whether the Online Purchase Intention Can Still Be Enhanced Even with Higher Search Costs and Perceived Risk

The purpose of this study was to explore the impact of search costs and perceived risk to online buying intention under the moderators of rarity and mental accounting in marketing practices. In this study, four types of online products food, toys, travelling and clothing were divided into pre-test and post-test to observe the rarity and mental accounting conditions. To investigate this study a survey was conducted with a sample size of 473 college students. The results found that (1) without moderators, search costs and perceived risk had no significant effects on purchase intention but had a positive significant effect on purchase intention under the interruptive effects of rarity and mental accounting. (2) In rarity moderator, online customers are more sensitive to limited time than limited quantity. (3) In mental accounting interruption, pay less and get more had significant moderating effects. (4) Limited time and get more had the highest contribution to an improvement in purchase intention. Contributions of this study provide to relevant businesses or network operators considerations of rarity and mental accounting in online promotion strategy implementation.

Severe extinction and rapid recovery of mammals across the Cretaceous-Palaeogene boundary, and the effects of rarity on patterns of extinction and recovery.

The end-Cretaceous mass extinction ranks among the most severe extinctions of all time; however, patterns of extinction and recovery remain incompletely understood. In particular, it is unclear how severe the extinction was, how rapid the recovery was and how sampling biases might affect our understanding of these processes. To better understand terrestrial extinction and recovery and how sampling influences these patterns, we collected data on the occurrence and abundance of fossil mammals to examine mammalian diversity across the K-Pg boundary in North America. Our data show that the extinction was more severe and the recovery more rapid than previously thought. Extinction rates are markedly higher than previously estimated: of 59 species, four survived (93% species extinction, 86% of genera). Survival is correlated with geographic range size and abundance, with widespread, common species tending to survive. This creates a sampling artefact in which rare species are both more vulnerable to extinction and less likely to be recovered, such that the fossil record is inherently biased towards the survivors. The recovery was remarkably rapid. Within 300000years, local diversity recovered and regional diversity rose to twice Cretaceous levels, driven by increased endemicity; morphological disparity increased above levels observed in the Cretaceous. The speed of the recovery tends to be obscured by sampling effects; faunas show increased endemicity, such that a rapid, regional increase in diversity and disparity is not seen in geographically restricted studies. Sampling biases that operate against rare taxa appear to obscure the severity of extinction and the pace of recovery across the K-Pg boundary, and similar biases may operate during other extinction events.

What Makes a Human Brand Authentic? Identifying the Antecedents of Celebrity Authenticity

ABSTRACTWhile authenticity has received considerable attention in the marketing literature, the factors that influence the perceived authenticity of a celebrity's “human brand” have remained unexplored. This research fills this void by identifying the antecedents of celebrity authenticity, defined as the perception that a celebrity behaves according to his or her true self. Based on a qualitative analysis of an open‐ended survey completed by 218 adults and on previous authenticity literature and attribution theory, the authors propose two antecedents of celebrity authenticity—rarity and stability—that are each composed of three sub‐dimensions. Analyses of cross‐sectional survey data from a sample of 428 adults provide support for the hypotheses that stability and rarity positively influence celebrity authenticity. Additionally, based on aging stability theory, the authors predict and demonstrate that the effects of rarity and stability on celebrity authenticity are moderated by age.

Upping their number, addressing their risk. Viola singularis (Violaceae) revisited, and an evaluation of sect. Andinium, its higher taxonomic group

An important amendment is made to the type locality given for Viola singularis. We analyse the precarious rarity of many Viola sect Andinium taxa, including this particular species. It is only known as a solitary specimen from a single site. The combined effect of rarity and geographical remoteness on the numerical content of the section is also discussed.

Conservation genetics of a rare Gerbil species: a comparison of the population genetic structures and demographic histories of the locally rare Pygmy Gerbil and the common Anderson's Gerbil

BackgroundOne of the major challenges in evolutionary biology is identifying rare species and devising management plans to protect them while also sustaining their genetic diversity. However, in attempting a broad understanding of rarity, single-species studies provide limited insights because they do not reveal whether the factors that affect rare species differ from those that affect more common species. To illustrate this important concept and to arrive at a better understanding of the form of rarity characterizing the rare Gerbillus henleyi, we explored its population genetic structure alongside that of the locally common Gerbillus andersoni allenbyi. We trapped gerbils in several locations in Israel's western and inner Negev sand dunes. We then extracted DNA from ear samples, and amplified two mitochondrial sequences: the control region (CR) and the cytochrome oxidase 2 gene (CO2).ResultsNucleotide diversity was low for all sequences, especially for the CR of G. a. allenbyi, which showed no diversity. We could not detect any significant population genetic structure in G. henleyi. In contrast, G. a. allenbyi's CO2 sequence showed significant population genetic structure. Pairwise PhiPT comparisons showed low values for G. henleyi but high values for G. a. allenbyi. Analysis of the species' demographic history indicated that G. henleyi's population size has not changed recently, and is under the influence of an ongoing bottleneck. The same analysis for G. a. allenbyi showed that this species has undergone a recent population expansion.ConclusionsComparing the two species, the populations of G. a. allenbyi are more isolated from each other, likely due to the high habitat specificity characterizing this species. The bottleneck pattern found in G. henleyi may be the result of competition with larger gerbil species. This result, together with the broad habitat use and high turnover rate characterizing G. henleyi, may explain the low level of differentiation among its populations. The evidence for a recent population expansion of G. a. allenbyi fits well with known geomorphological data about the formation of the Negev sand dunes and paleontological data about this species' expansion throughout the Levant. In conclusion, we suggest that adopting a comparative approach as presented here can markedly improve our understanding of the causes and effects of rarity, which in turn can allow us to better protect biodiversity patterns.

The effects of rarity and abundance distributions on measurements of local morphological disparity

Understanding the relationships between morphological disparity and environment, geography, and scale require examination at the local level. Even with disparity metrics that are inherently sample size independent, the nature of rare species and the segregation of common and rare species within morphospace can create substantial sampling issues. Eight well-sampled, Late Ordovician crinoid assemblages were examined for potential biases in the study of local disparity. Disparity is based on the ordination of discrete characters. The rare and common species within these assemblages contributed equally to disparity. In spite of this pattern, rare species in some localities occupy a different area of morphospace, causing disparity to vary greatly with sampling intensity. Morphological rarefaction based on the number of specimens shows that disparity weighted by abundance is constant past a sample size of approximately 30 individuals. This metric is dependent on the evenness within an assemblage as well as the abundance within subgroups in morphospace. Disparity weighted according to abundance gives a view of the functional disparity of an assemblage, which is more applicable in studies of local disparity, though unweighted disparity is still preferred in regional-scale studies and in investigations of morphospace filling through a clade's history.

Rarity, pseudodiagnosticity and Bayesian reasoning

Three experiments investigated the effect of rarity on people's selection and interpretation of data in a variant of the pseudodiagnosticity task. For familiar (Experiment 1) but not for arbitrary (Experiment 3) materials, participants were more likely to select evidence so as to complete a likelihood ratio when the initial evidence they received was a single likelihood concerning a rare feature. This rarity effect with familiar materials was replicated in Experiment 2 where it was shown that participants were relatively insensitive to explicit manipulations of the likely diagnosticity of rare evidence. In contrast to the effects for data selection, there was an effect of rarity on confidence ratings after receipt of a single likelihood for arbitrary but not for familiar materials. It is suggested that selecting diagnostic evidence necessitates explicit consideration of the alternative hypothesis and that consideration of the possible consequences of the evidence for the alternative weakens the rarity effect in confidence ratings. Paradoxically, although rarity effects in evidence selection and confidence ratings are in the spirit of Bayesian reasoning, the effect on confidence ratings appears to rely on participants thinking less about the alternative hypothesis.