نتایج جستجو برای: population size

تعداد نتایج: 1199768  

2016
Nina Cedergreen Nils Jakob Nørhave Claus Svendsen David J. Spurgeon Jonathan H Freedman

A wealth of studies has investigated how chemical sensitivity is affected by temperature, however, almost always under different constant rather than more realistic fluctuating regimes. Here we compared how the nematode Caenorhabditis elegans responds to copper at constant temperatures (8-24°C) and under fluctuation conditions of low (±4°C) and high (±8°C) amplitude (averages of 12, 16, 20°C an...

1997
Glen Meeden

1 Interval estimators for the population mean for skewed distributions with a small sample size SUMMARY In nite population sampling it has long been known that for small sample sizes, when sampling from a skewed population, the usual frequentist intervals for the population mean cover the true value less often than their stated frequency of coverage. Recently a noninformative Bayesian approach ...

2008
Alex Z. Fu Michael W. Kattan

Objective: Several estimators exist when average utility scores are not available for patient populations with multiple disease conditions. The multiplicative estimator is a widespread choice among them. Our study is to empirically test the accuracy of the multiplicative estimator and compare it with other estimators. Methods: The Medical Expenditure Panel Survey (MEPS) has a nationally represe...

2001
CAMERON L. ALDRIDGE MARK BRIGHAM

In Canada, Greater Sage-Grouse (Centrocercus urophasianus) are at the northern edge of their range, occurring only in southeastern Alberta and southwestern Saskatchewan. The population in Canada has declined by 66% to 92% over the last 30 years. We used radio-telemetry to follow 20 female Greater Sage-Grouse and monitor productivity in southeastern Alberta, and to assess habitat use at nesting ...

Journal: :Molecular biology and evolution 2002
Sebastian E Ramos-Onsins Julio Rozas

A number of statistical tests for detecting population growth are described. We compared the statistical power of these tests with that of others available in the literature. The tests evaluated fall into three categories: those tests based on the distribution of the mutation frequencies, on the haplotype distribution, and on the mismatch distribution. We found that, for an extensive variety of...

Journal: :Genetics 2003
Mark A Beaumont

This article introduces a new general method for genealogical inference that samples independent genealogical histories using importance sampling (IS) and then samples other parameters with Markov chain Monte Carlo (MCMC). It is then possible to more easily utilize the advantages of importance sampling in a fully Bayesian framework. The method is applied to the problem of estimating recent chan...

2015
Anna Goodman Ilona Koupil

Studying biological and social determinants of mortality and fertility provides insight into selective pressures in a population and the possibility of trade-offs between shortand long-term reproductive success. Limited data is available from post-demographic transition populations. We studied determinants of reproductive success using multi-generational data from a large, population-based coho...

Journal: :Evolution; international journal of organic evolution 2007
Ryan Calsbeek Thomas B Smith

Anolis lizards in the Greater Antilles are thought to have diversified through natural selection on body size and shape, presumably due to interspecific competition and variation in locomotor performance. Here we measure natural selection on body size over three years and across seven replicate populations of the brown anole, A. sagrei. We experimentally manipulated an important component of th...

2008
Robert S. Walker Marcus J. Hamilton

Previous attempts to explain variation in human growth and development emphasize the energetic constraints imposed by malnutrition and disease. However, this approach does not address the evolutionary effects of mortality risk on ontogenetic variation, a common theme in life-history studies. The conventional approach can be reconciled with life-history theory by considering the effect of mortal...

2010

The sample size of a statistical sample is the number of observations that constitute it. It is typically denoted n, a positive integer (natural number). Typically, all else being equal, a larger sample size leads to increased precision in estimates of various properties of the population. This can be seen in such statistical rules as the law of large numbers and the central limit theorem. Repe...

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