Sample size in studies of geographic variation

1981 ◽  
Vol 59 (11) ◽  
pp. 2158-2159
Author(s):  
K. W. Newman ◽  
R. C. Jancey
Keyword(s):  
Sample Size ◽  
Geographic Variation ◽  
Pinus Contorta ◽  
Objective Basis ◽  
Number Of Individuals

A procedure is described which provides an objective basis for selecting the number of individuals to sample at each location in studies of geographic variation within species. An example is given using cone data for Pinus contorta.

Minimum Numbers and Sample Size in Vertebrate Faunal Analysis

1978 ◽  
Vol 43 (1) ◽  
pp. 53-65 ◽  
Author(s):  
Donald K. Grayson
Keyword(s):  
Sample Size ◽  
Faunal Analysis ◽  
Minimum Number ◽  
Minimum Number Of Individuals ◽  
Minimum Numbers ◽  
Number Of Individuals ◽  
The Relationship

Of the measures currently available for quantifying the abundance of taxa within archaeological and paleontological vertebrate faunas, the minimum number of individuals per taxon is most frequently employed. This paper explores the relationship between the minimum number of individuals (MNI) calculated for a given taxon and the number of specimens (E) from which these values were calculated. Several approaches for controlling for the complex interrelationships between MNI and E are advanced and discussed.

scholarly journals An Effective Sample Size for Predicting Plant Disease Incidence in a Spatial Hierarchy

1999 ◽  
Vol 89 (9) ◽  
pp. 770-781 ◽  
Author(s):  
L. V. Madden ◽  
G. Hughes
Keyword(s):  
Sample Size ◽  
Binomial Distribution ◽  
Disease Incidence ◽  
Simulated Data ◽  
Heterogeneous Data ◽  
Sampling Unit ◽  
Effective Sample Size ◽  
Incidence Data ◽  
Eutypa Dieback ◽  
Number Of Individuals

For aggregated or heterogeneous disease incidence, one can predict the proportion of sampling units diseased at a higher scale (e.g., plants) based on the proportion of diseased individuals and heterogeneity of diseased individuals at a lower scale (e.g., leaves) using a function derived from the beta-binomial distribution. Here, a simple approximation for the beta-binomial-based function is derived. This approximation has a functional form based on the binomial distribution, but with the number of individuals per sampling unit (n) replaced by a parameter (v) that has similar interpretation as, but is not the same as, the effective sample size (ndeff ) often used in survey sampling. The value of v is inversely related to the degree of heterogeneity of disease and generally is intermediate between ndeff and n in magnitude. The choice of v was determined iteratively by finding a parameter value that allowed the zero term (probability that a sampling unit is disease free) of the binomial distribution to equal the zero term of the beta-binomial. The approximation function was successfully tested on observations of Eutypa dieback of grapes collected over several years and with simulated data. Unlike the beta-binomial-based function, the approximation can be rearranged to predict incidence at the lower scale from observed incidence data at the higher scale, making group sampling for heterogeneous data a more practical proposition.

scholarly journals Evaluating the estimation of genetic correlation and heritability using summary statistics

2021 ◽  
Author(s):  
Ju Zhang ◽  
Fredrick R. Schumacher
Keyword(s):  
Sample Size ◽  
Genetic Correlation ◽  
Reference Panel ◽  
Summary Statistics ◽  
External Reference ◽  
Size Number ◽  
Admixed Population ◽  
Statistical Approaches ◽  
Panel Summary ◽  
Number Of Individuals

AbstractWhile novel statistical methods quantifying the shared heritability of traits and diseases between ancestral distinct populations have been recently proposed, a thorough evaluation of these approaches under differing circumstances remain elusive. Brown et al.2016 proposed the method Popcorn to estimate the shared heritability, i.e. genetic correlation, using only summary statistics. Here, we evaluate Popcorn under several parameters and circumstances: sample size, number of SNPs, sample size of external reference panel, various population pairs, inappropriate external reference panel, and admixed population involved. Our results determined the minimum sample size of the external reference panel, summary statistics, and number of SNPs required to accurately estimate both the genetic correlation and heritability. Moreover, the number of individuals and SNPs required to produce accurate and stable estimates was directly proportional with heritability in Popcorn. Misrepresentation of the reference panel overestimated the genetic correlation by 20% and heritability by 60%. Lastly, applying Popcorn to homogeneous (EUR) and admixed (ASW) populations underestimated the genetic correlation by 15%. Although statistical approaches estimating the shared heritability between ancestral populations will provide novel etiologic insight, caution is required ensuring results are based on the appropriate sample size, number of SNPs, and the generalizability of the reference panel to the discovery populations.

scholarly journals Sample Sizes Needed to Describe Length-Frequency of Small-Bodied Fishes: An Example Using Larval Pacific Lamprey

2016 ◽  
Vol 7 (2) ◽  
pp. 315-322 ◽  
Author(s):  
Luke D. Schultz ◽  
Mariah P. Mayfield ◽  
Steven L. Whitlock
Keyword(s):  
Data Collection ◽  
Sample Size ◽  
Length Distribution ◽  
Fish Population ◽  
Anadromous Fish ◽  
Western North America ◽  
Sample Sizes ◽  
Length Frequency ◽  
Pacific Lamprey ◽  
Number Of Individuals

Abstract The ability to describe the length distribution of a fish population requires sampling an adequate number of individuals, but collecting more fish than needed is inefficient. While fisheries managers have assessed sample size requirements for many sport fishes, these requirements are not routinely described for small-bodied fishes (i.e., maximum length ≤200 mm), particularly larval lampreys. To improve the efficiency of data collection for these fishes, we used resampling analyses to asses sample size requirements for accurately describing length distributions of larval (freshwater-dwelling) Pacific lamprey Entosphenus tridentatus, an anadromous fish native to western North America (total length 60–156 mm). We found that the highest increases in accuracy occurred with sample sizes <50, and that we needed sample sizes of 40 to 130 to describe length frequency with 95% confidence, depending on length interval used for performing length-frequency analyses. From these results, we recommend collecting 100 individuals if using 5-mm length intervals to examine length frequency of larval lamprey. These findings can also be used to estimate the relative accuracy of sample sizes in existing assessments and develop and refine monitoring programs for larval lampreys and other small-bodied fishes.

Temporal Changes of Allele Frequency in Pacific Salmon: Implications for Mixed-Stock Fishery Analysis

1990 ◽  
Vol 47 (5) ◽  
pp. 968-976 ◽  
Author(s):  
Robin S. Waples
Keyword(s):  
Sample Size ◽  
Allele Frequency ◽  
Genetic Drift ◽  
Pacific Salmon ◽  
Sampling Strategy ◽  
Effective Sample Size ◽  
Multiple Sampling ◽  
Effective Number Of Breeders ◽  
Mixed Stock ◽  
Number Of Individuals

The effects of temporal variation in allele frequency on mixed-stock fishery analysis of Pacific salmon (Oncorhynchus spp.) are examined. The concept of effective sample size (Se), which equates the precision obtained from a sample from a finite population with that from one with no temporal variability, is used to evaluate the magnitude of the problems introduced by genetic drift. Results from simulations modeling the overlapping year-class pattern typical of chinook salmon (O. tshawytscha) indicate that the ratio of effective to actual sample size (Se/S) is determined primarily by the ratio of sample size to the effective number of breeders per year (S/Nb). Unless Nb is large relative to S, effective sample size can be considerably less than the actual number of individuals sampled. Sampling in more than 1 yr results in a higher Se than does taking the same total number of individuals in 1 yr; furthermore, the advantages to multiple sampling are greatest in small populations, in which the effects of genetic drift are most pronounced. By choosing an appropriate sampling strategy, the sources of uncertainty in the analysis attributable to genetic drift can be reduced below any arbitrary level.

STATISTICAL METHODS IN MEDICAL RESEARCH II. SAMPLE SIZES REQUIRED IN EXPERIMENTS INVOLVING ALL-OR-NONE RESPONSES

1953 ◽  
Vol 31 (5) ◽  
pp. 406-416 ◽  
Author(s):  
Donald Mainland ◽  
Marion I. Sutcliffe
Keyword(s):  
Medical Research ◽  
Sample Size ◽  
Statistical Methods ◽  
Treatment Effects ◽  
Reliable Estimate ◽  
Sample Sizes ◽  
Size Number ◽  
Different Types ◽  
Experimental Treatments ◽  
Number Of Individuals

In order to obtain a reliable estimate of the sample size (number of individuals) required in an experiment, an investigator must first specify: (1) what risk he is willing to run of mistakenly concluding that his different experimental treatments have produced different effects; (2) what the magnitude of the effect produced by one of the treatments is likely to be; (3) what magnitude of difference between treatment effects would be important to him; (4) what risk he is willing to run of failing to detect a difference when it is of that magnitude—the risk of an unsuccessful experiment. Difficulties in answering these questions are discussed with reference to five examples from different types of medical research. For experiments involving the comparison of two treatments that produce an all-or-none effect such as death or survival, a table derived from binomial expansions is presented, which, for samples containing up to 100 individuals, shows the probabilities of successful experiments for different magnitudes of treatment effects.

scholarly journals Sample size requirements for genetic studies on yellowfin tuna

PLoS ONE ◽  
2021 ◽  
Vol 16 (11) ◽  
pp. e0259113
Author(s):  
Scott D. Foster ◽  
Pierre Feutry ◽  
Peter Grewe ◽  
Campbell Davies
Keyword(s):  
Sample Size ◽  
Simulated Data ◽  
Ocean Basin ◽  
Yellowfin Tuna ◽  
Sampling Location ◽  
Nucleotide Polymorphisms ◽  
Sampling Locations ◽  
Basin Scale ◽  
Genetic Profiles ◽  
Number Of Individuals

In population genetics, the amount of information for an analytical task is governed by the number of individuals sampled and the amount of genetic information measured on each of those individuals. In this work, we assessed the numbers of individual yellowfin tuna (Thunnus albacares) and genetic markers required for ocean-basin scale inferences. We assessed this for three distinct data analysis tasks that are often employed: testing for differences between genetic profiles; stock delineation, and; assignment of individuals to stocks. For all analytical tasks, we used real (not simulated) data from four sampling locations that span the tropical Pacific Ocean. Whilst spatially separated, the genetic differences between the sampling sites were not substantial, a maximum of approximately Fst = 0.02, which is quite typical of large pelagic fish. We repeatedly sub-sampled the data, mimicking a new survey, and performed the analyses. False positive rates were also assessed by re-sampling and randomly assigning fish to groups. Varying the sample sizes indicated that some analytical tasks, namely profile testing, required relatively few individuals per sampling location (n ≳ 10) and single nucleotide polymorphisms (SNPs, m ≳ 256). Stock delineation required more individuals per sampling location (n ≳ 25). Assignment of fish to sampling locations required substantially more individuals, more in fact than we had available (n > 50), although this sample size could be reduced to n ≳ 30 when individual fish were assumed to belong to one of the groups sampled. With these results, designers of molecular ecological surveys for yellowfin tuna, and users of information from them, can assess whether the information content is adequate for the required inferential task.

Perceptual Learning of Vocoded Speech With and Without Contralateral Hearing: Implications for Cochlear Implant Rehabilitation

2020 ◽  
pp. 1-10
Author(s):  
Martin Chavant ◽  
Alexis Hervais-Adelman ◽  
Olivier Macherey
Keyword(s):  
Cochlear Implant ◽  
Perceptual Learning ◽  
Speech Signal ◽  
Training Phase ◽  
Monosyllabic Words ◽  
Low Pass ◽  
Contralateral Ear ◽  
Number Of Individuals ◽  
Insight Into ◽  
Vocoded Speech

Purpose An increasing number of individuals with residual or even normal contralateral hearing are being considered for cochlear implantation. It remains unknown whether the presence of contralateral hearing is beneficial or detrimental to their perceptual learning of cochlear implant (CI)–processed speech. The aim of this experiment was to provide a first insight into this question using acoustic simulations of CI processing. Method Sixty normal-hearing listeners took part in an auditory perceptual learning experiment. Each subject was randomly assigned to one of three groups of 20 referred to as NORMAL, LOWPASS, and NOTHING. The experiment consisted of two test phases separated by a training phase. In the test phases, all subjects were tested on recognition of monosyllabic words passed through a six-channel “PSHC” vocoder presented to a single ear. In the training phase, which consisted of listening to a 25-min audio book, all subjects were also presented with the same vocoded speech in one ear but the signal they received in their other ear differed across groups. The NORMAL group was presented with the unprocessed speech signal, the LOWPASS group with a low-pass filtered version of the speech signal, and the NOTHING group with no sound at all. Results The improvement in speech scores following training was significantly smaller for the NORMAL than for the LOWPASS and NOTHING groups. Conclusions This study suggests that the presentation of normal speech in the contralateral ear reduces or slows down perceptual learning of vocoded speech but that an unintelligible low-pass filtered contralateral signal does not have this effect. Potential implications for the rehabilitation of CI patients with partial or full contralateral hearing are discussed.

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