Accuracy of Subsampling for Height Measurements in Loblolly Pine Plots

Abstract Estimating heights in research and inventory plots is costly. We examined the feasibility of subsampling tree heights as opposed to measuring all trees. Four sampling intensities (75, 50, 25, and 10%) and four sampling strategies (systematic sampling, simple random sampling without replacement, stratified sampling across the diameter distribution, and sampling the first trees in each plot) were investigated. Data from 600 loblolly pine plots in fertilizer trials in the southeastern United States were used. The application of a height–dbh regression to predict the heights of unmeasured trees was also investigated. Sampling the first trees generally resulted in poorer estimates than the other sampling schemes. Systematic and simple random sampling performed similarly. A 50% sampling intensity with either systematic or simple random sampling and a height–dbh regression predicting the heights of unmeasured trees estimated more than 90% of plots to within 2.2% of the observed plot height and more than 94% of plots to within 2.5% of the observed volume, and they were more accurate than the stratified sampling at the same intensity. Systematic sampling is easy to implement, requiring no prior plot knowledge. We conclude that a 50% systematic sampling combined with a height–dbh regression will reduce costs without compromising accuracy.

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Comparison of Variance Estimators for Systematic Environmental Sample Surveys: Considerations for Post-Stratified Estimation

Forests ◽

10.3390/f12060772 ◽

2021 ◽

Vol 12 (6) ◽

pp. 772

Author(s):

Bryce Frank ◽

Vicente J. Monleon

Keyword(s):

Random Sampling ◽

Simple Random Sampling ◽

National Forest Inventory ◽

Point Estimation ◽

Systematic Sampling ◽

Sampling Variance ◽

Variance Estimators ◽

The Past ◽

Point Estimators ◽

Species Specific

The estimation of the sampling variance of point estimators under two-dimensional systematic sampling designs remains a challenge, and several alternative variance estimators have been proposed in the past few decades. In this work, we compared six alternative variance estimators under Horvitz-Thompson (HT) and post-stratification (PS) point estimation regimes. We subsampled a multitude of species-specific forest attributes from a large, spatially balanced national forest inventory to compare the variance estimators. A variance estimator that assumes a simple random sampling design exhibited positive relative bias under both HT and PS point estimation regimes ranging between 1.23 to 1.88 and 1.11 to 1.78 for HT and PS, respectively. Alternative estimators reduced this positive bias with relative biases ranging between 1.01 to 1.66 and 0.90 to 1.64 for HT and PS, respectively. The alternative estimators generally obtained improved efficiencies under both HT and PS, with relative efficiency values ranging between 0.68 to 1.28 and 0.68 to 1.39, respectively. We identified two estimators as promising alternatives that provide clear improvements over the simple random sampling estimator for a wide variety of attributes and under HT and PS estimation regimes.

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Bayesian Analysis of Finite Populations under Simple Random Sampling

Entropy ◽

10.3390/e23030318 ◽

2021 ◽

Vol 23 (3) ◽

pp. 318

Author(s):

Manuel Mendoza ◽

Alberto Contreras-Cristán ◽

Eduardo Gutiérrez-Peña

Keyword(s):

Bayesian Analysis ◽

Random Sampling ◽

Simple Random Sampling ◽

Survey Sampling ◽

Finite Populations ◽

Population Means ◽

Sampling Schemes ◽

Nonparametric Approach ◽

Conventional Procedure ◽

Continuous And Discrete Variables

Statistical methods to produce inferences based on samples from finite populations have been available for at least 70 years. Topics such as Survey Sampling and Sampling Theory have become part of the mainstream of the statistical methodology. A wide variety of sampling schemes as well as estimators are now part of the statistical folklore. On the other hand, while the Bayesian approach is now a well-established paradigm with implications in almost every field of the statistical arena, there does not seem to exist a conventional procedure—able to deal with both continuous and discrete variables—that can be used as a kind of default for Bayesian survey sampling, even in the simple random sampling case. In this paper, the Bayesian analysis of samples from finite populations is discussed, its relationship with the notion of superpopulation is reviewed, and a nonparametric approach is proposed. Our proposal can produce inferences for population quantiles and similar quantities of interest in the same way as for population means and totals. Moreover, it can provide results relatively quickly, which may prove crucial in certain contexts such as the analysis of quick counts in electoral settings.

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AGROFORESTRI BERBASIS ROTAN TERHADAP SOSIAL EKONOMI MASYARAKAT DI BARITO SELATAN

Jurnal Hutan Tropis ◽

10.20527/jht.v4i1.2886 ◽

2017 ◽

Vol 4 (1) ◽

pp. 93

Author(s):

Johanna Maria Rotinsulu ◽

Sosilawaty Sosilawaty ◽

Yanarita Yanarita

Keyword(s):

Random Sampling ◽

Sampling Methods ◽

Simple Random Sampling ◽

The Other ◽

Average Yield ◽

Natural Conditions ◽

Central Kalimantan ◽

Economic Level ◽

The Village ◽

Society Research

South Barito is an area of rattan and rattan production center of the province of Central Kalimantan, on the other hand is one area that has natural conditions very conducive to the development of rattan. This study reveals how patterns in addition to planting and processing of rattan traditionally also analyze the socio-economic level of society. Research conducted in South Barito regency, District Karau in Two Villages is Bangkuang and New Salat. The village of the second sample is determined gardens and population are farmers who cultivate cane with sampling methods by simple random sampling, because the peasant population is homogeneous, the number of samples in each village 34 respondents or 68 farmers overall. The result showed that in general the rattan garden where the studies were not well-maintained, where the average of respondents (45%) said that maintenance is only performed at the time of going to the harvesting or one for rattan planting. Besides the low price of rattan is led to a reduction of land management / rattan gardens intensively. and production of rattan average yield of 2.6 tons ha-1 or 245.5 clumps of cane ha-1. For the villagers of business administration studies despite conditions that are considered less favorable, but they still look forward to the Government's policy to remain aligned to the Farmers Rattan. In addition, because cane is inherited and used as a hallmark of South Barito society in general.Barito Selatan merupakan daerah penghasil rotan dan sentra produksi rotan provinsi Kalimantan Tengah, selain itu merupakan salah satu wilayah yang memiliki kondisi alam yang sangat mendukung bagi perkembangan rotan. Penelitian ini selain untuk mengungkapkan bagaimana pola tanam dan pengolahan rotan secara tradisional juga menganalisis tingkat sosial ekonomi masyarakat. Penelitian dilaksanakan di Kabupaten Barito Selatan, Kecamatan Karau di Dua Desa yaitu Bangkuang dan Salat Baru. Dari kedua Desa tersebut ditentukan kebun sampel dan populasi masyarakat yaitu petani yang mengusahakan rotan dengan metode pengambilan sampel secara simple random sampling, karena populasi petani bersifat homogen, jumlah sampel di masing-masing desa 34 responden atau keseluruhan 68 petani. Dari hasil penelitian diperoleh bahwa pada umumnya kebun rotan di tempat penelitian tersebut tidak terpelihara dengan baik, dimana rata-rata responden (45%) menyebutkan bahwa pemeliharaan hanya dilakukan pada saat akan dilakukan pemanenan atau satu kali selama rotan itu di tanam. Selain itu rendahnya harga rotan sangat berdampak pada berkurangnya pengelolaan lahan/kebun rotan secara intensif. dan hasil produksi rotan rata-rata diperoleh 2,6 ton ha-1 atau 245,5 rumpun rotan ha-1. Bagi masyarakat Desa studi walaupun kondisi tataniaga yang dianggap kurang menguntungkan, namun mereka masih berharap kebijakan Pemerintah tetap berpihak kepada Petani Rotan. Di samping itu karena pada umumnya rotan merupakan warisan dan digunakan sebagai ciri khas masyarakat Barito Selatan.

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Analysis of the Impact of the Type of Sampling of Representative Properties on the Results of Mass Appraisal

Folia Oeconomica Stetinensia ◽

10.2478/foli-2020-0041 ◽

2020 ◽

Vol 20 (2) ◽

pp. 152-167

Author(s):

Sebastian Gnat

Keyword(s):

Real Estate ◽

Random Sampling ◽

Simple Random Sampling ◽

Multiple Regression Model ◽

Stratified Sampling ◽

Sampling Errors ◽

Real Estate Valuation ◽

Simple Sampling ◽

The Impact ◽

Mean Square Errors

Abstract Research background: Mass valuation is a process in which many properties are valued simultaneously with a uniform approach. An example of a procedure used for mass real estate valuation is the Szczecin Algorithm of Real Estate Mass Appraisal (SAREMA), which can be developed into a multiple regression model. The algorithm is based on a set of drawn representative properties. This set determines, inter alia, the quality of obtained valuations. Purpose: The objective of the study is to verify the hypothesis whether changing the method of sampling representative properties from the originally used simple random sampling to stratified sampling improves the results of the SAREMA econometric variant. Research methodology: The article presents a study that uses two methods of representative properties sampling – simple random sampling and stratified sampling. Errors of the models of valuation created taking into account both methods of sampling and different number of representative properties are compared. A key aspect of the survey is the choice of a better sampling method. Results: The study has shown that stratified sampling improves valuation results and, more specifically, allows for lower root mean square errors. Stratified sampling yielded better results in the initial phase of the study with more observations, but reducing the percentage of strata participating in the draws, despite the increase in RMSE, guaranteed lower errors than the corresponding results based on simple sampling in all variants of the study. Novelty: The article confirms the possibility of improving the results of mass property valuation by changing the scheme of representative properties sampling. The results allowed for the conclusion that stratified sampling is a better way of creating a set of representative properties.

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Statistical Uncertainty Analyses of Void Fraction Predictions Using Two Different Sampling Strategies: Latin Hypercube and Simple Random Sampling

18th International Conference on Nuclear Engineering: Volume 4, Parts A and B ◽

10.1115/icone18-30096 ◽

2010 ◽

Cited By ~ 1

Author(s):

Augusto Hernandez-Solis ◽

Christian Ekberg ◽

Arvid O¨dega˚rd Jensen ◽

Christophe Demaziere ◽

Ulf Bredolt

Keyword(s):

Steady State ◽

Sample Size ◽

Void Fraction ◽

Random Sampling ◽

Simple Random Sampling ◽

Statistical Uncertainty ◽

Sampling Strategies ◽

Latin Hypercube ◽

Fine Mesh ◽

Uncertainty Analyses

In recent years, a more realistic safety analysis of nuclear reactors has been based on best estimate (BE) computer codes. Because their predictions are unavoidably affected by conceptual, aleatory and experimental sources of uncertainty, an uncertainty analysis is needed if useful conclusions are to be obtained from BE codes. In this paper, statistical uncertainty analyses of cross-sectional averaged void fraction calculations using the POLCA-T system code, and based on the BWR Full-Size Fine-Mesh Bundle Test (BFBT) benchmark are presented by means of two different sampling strategies: Latin Hypercube (LHS) and Simple Random Sampling (SRS). LHS has the property of densely stratifying across the range of each input probability distribution, allowing a much better coverage of the input uncertainties than SRS. The aim here is to compare both uncertainty analyses on the BWR assembly void axial profile prediction in steady-state, and on the transient void fraction prediction at a certain axial level coming from a simulated re-circulation pump trip scenario. It is shown that the replicated void fraction mean (either in steady-state or transient conditions) has less variability when using LHS than SRS for the same number of calculations (i.e. same input space sample size) even if the resulting void fraction axial profiles are non-monotonic. It is also shown that the void fraction uncertainty limits achieved with SRS by running 458 calculations (sample size required to cover 95% of 8 uncertain input parameters with a 95% confidence), result in the same uncertainty limits achieved by LHS with only 100 calculations. These are thus clear indications on the advantages of using LHS.

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An examination of the placement of adverbials in the academic writing of fresh undergraduate students in the University of Cape Coast, Ghana

EJOTMAS Ekpoma Journal of Theatre and Media Arts ◽

10.4314/ejotmas.v7i1-2.8 ◽

2020 ◽

Vol 7 (1-2) ◽

pp. 110-128

Author(s):

Philip Arthur Gborsong ◽

Anita B. Appartaim

Keyword(s):

Second Language ◽

Research Design ◽

Undergraduate Students ◽

Academic Writing ◽

Random Sampling ◽

Quantitative Research ◽

Simple Random Sampling ◽

The Other ◽

Cape Coast ◽

The University

Rules have been formulated on how adverbials are used. Such rules as stated by Quirk and Greenbaum (1973), Hornby (1975) and Swan (1995) are silent on how a few adverbials that have no restrictions regarding their position and order in sentences should be used. This paper, relying on language variation in the second language setting as a theoretical framework, explored how undergraduate students used these kinds of mobile adverbials. The quantitative research design and a simple random sampling were applied to select a total of 100 essays and exercises from fresh undergraduates of the University of Cape Coast, Ghana. Analysing these essays and exercises, we concluded that although the adverbial is an optional clausal element, the undergraduate students used it in providing further information on the other clausal elements. In addition, the undergraduate students often placed the adverbials in the mid position of their sentences. Keywords: Adverbials, GE, Undergraduate students, Clausal elements, Effective communication

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Geographically Stratified Importance Sampling for the Calibration of Aggregated Destination Choice Models for Trip Distribution

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198105193500110 ◽

2005 ◽

Vol 1935 (1) ◽

pp. 85-92 ◽

Cited By ~ 3

Author(s):

Min-Tang Li ◽

Lee-Fang Chow ◽

Fang Zhao ◽

Shi-Chiang Li

Keyword(s):

Importance Sampling ◽

Random Sampling ◽

Sampling Strategy ◽

Simple Random Sampling ◽

Choice Models ◽

Stratified Sampling ◽

Destination Choice ◽

Selection Probabilities ◽

Choice Probabilities ◽

Choice Set

A key feature in estimating and applying destination choice models with aggregate alternatives is to sample a set of nonchosen traffic analysis zones (TAZs), plus the one a trip maker chose, to construct a destination choice set. Computational complexity is reduced because the choice set would be too large if all study area TAZs were included in the calibration. Commonly, two types of sampling strategies are applied to draw subsets of alternatives from the universal choice set. The first, and simplest, approach is to select randomly a subset of nonchosen alternatives with uniform selection probabilities and then add the chosen alternative if it is not otherwise included. The approach, however, is not an efficient sampling scheme because most alternatives for a given trip maker may have small choice probabilities. The second approach, stratified importance sampling, draws samples with unequal selection probabilities determined on the basis of preliminary estimates of choice probabilities for every alternative in the universal choice set. The stratified sampling method assigns different selection probabilities to alternatives in different strata. Simple random sampling is applied to draw alternatives in each stratum. However, it is unclear how to divide the study area so that destination TAZs may be sampled effectively. The process of and findings from implementing a stratified sampling strategy in selecting alternative TAZs for calibrating aggregate destination choice models in a geographic information system (GIS) environment are described. In this stratified sampling analysis, stratum regions varied by spatial location and employment size in the adjacent area were defined for each study area TAZ. The sampling strategy is more effective than simple random sampling in regard to maximum log likelihood and goodness-of-fit values.

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PENENTUAN TINGKAT EFISIENSI ALOKATIF DAN EFISIENSI TEKNIS PADA USAHATANI JAGUNG MANIS ( Zea mays saccharata L. ) DI KECAMATAN KUPANG TIMUR

Buletin Ilmiah IMPAS ◽

10.35508/impas.v21i02.2632 ◽

2020 ◽

Vol 21 (2) ◽

pp. 180-189

Author(s):

Oktavia Oni ◽

Wiendiyati Wiendiyati ◽

Johanna Suek

Keyword(s):

Technical Efficiency ◽

Random Sampling ◽

Sweet Corn ◽

Allocative Efficiency ◽

Simple Random Sampling ◽

The Other ◽

Production Level ◽

Corn Production ◽

Production Factors ◽

Urea Production

Research about the determining of allocative and technical efficiency level of sweet corn farming in East Kupang Sub District aims to find out the effect of the use of production factors toward sweet corn production; to analyze the level of allocative efficiency of its use; and to analyze the level of production technical efficiency of sweet corn. The research location was chosen by purposive sampling with the consideration that Oesao village and Pukdale are villages where produce sweet corn in East Kupang Sub District. The sample of research respondents was taken by simple random sampling with 79 respondents consisting of 35 farmers from Oesao village and 44 farmers from Pukdale village. The collect of data had been carried out as long as February to March 2020. The reseach results showed that the factors of land, seed, and urea production significantly affected the production of sweet corn, while the factors of NPK, pesticides and labor production had no significant effect. The level of efficiency can be reached through allocate production inputs precisely. In this case, by reducing the use of land and urea fertilizer, on the other hand, by adding the use of seeds. Also, the farmer production level technically is not efficient yet with the average of actual production level is 10,408 grains or around 1,487 kg, while the average frontier production level is 28,146.64 grains or around 4,021 kg. There are 39 farmers who their technical efficiency in low level category, than, 28 farmers in moderate level category, and as many as 12 farmers have reached a level of technical efficiency.

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Survey design and analysis considerations when utilizing misclassified sampling strata

BMC Medical Research Methodology ◽

10.1186/s12874-021-01332-8 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Aya A. Mitani ◽

Nathaniel D. Mercaldo ◽

Sebastien Haneuse ◽

Jonathan S. Schildcrout

Keyword(s):

Ethnic Minorities ◽

Random Sampling ◽

Survey Design ◽

Simple Random Sampling ◽

Stratified Sampling ◽

Simple Random Sample ◽

Parameter Estimates ◽

Complex Survey ◽

Racial And Ethnic Minorities ◽

Complex Survey Design

Abstract Background A large multi-center survey was conducted to understand patients’ perspectives on biobank study participation with particular focus on racial and ethnic minorities. In order to enrich the study sample with racial and ethnic minorities, disproportionate stratified sampling was implemented with strata defined by electronic health records (EHR) that are known to be inaccurate. We investigate the effect of sampling strata misclassification in complex survey design. Methods Under non-differential and differential misclassification in the sampling strata, we compare the validity and precision of three simple and common analysis approaches for settings in which the primary exposure is used to define the sampling strata. We also compare the precision gains/losses observed from using a disproportionate stratified sampling scheme compared to using a simple random sample under varying degrees of strata misclassification. Results Disproportionate stratified sampling can result in more efficient parameter estimates of the rare subgroups (race/ethnic minorities) in the sampling strata compared to simple random sampling. When sampling strata misclassification is non-differential with respect to the outcome, a design-agnostic analysis was preferred over model-based and design-based analyses. All methods yielded unbiased parameter estimates but standard error estimates were lowest from the design-agnostic analysis. However, when misclassification is differential, only the design-based method produced valid parameter estimates of the variables included in the sampling strata. Conclusions In complex survey design, when the interest is in making inference on rare subgroups, we recommend implementing disproportionate stratified sampling over simple random sampling even if the sampling strata are misclassified. If the misclassification is non-differential, we recommend a design-agnostic analysis. However, if the misclassification is differential, we recommend using design-based analyses.

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Punctuation Errors in Writing: A Comparative Study of Students’ Performance from Different Pakistani Universities

sjesr ◽

10.36902/sjesr-vol3-iss1-2020(165-177) ◽

2020 ◽

Vol 3 (1) ◽

pp. 165-177

Author(s):

Dr. Syed Shujaat Ali ◽

Mr. Tariq Amin ◽

Mr. Muhammad Ishtiaq

Keyword(s):

Mixed Method ◽

Random Sampling ◽

Corrective Feedback ◽

Sampling Technique ◽

Simple Random Sampling ◽

The Other ◽

Mixed Method Research ◽

Analysis Technique ◽

Different Types ◽

National University

The study aimed at exploring the different types of punctuation errors made by students in their writings, the reasons behind these errors, and the reasons behind the differences in the frequency of punctuation errors made by students from two different sets of universities, with one set belonging to backward areas and the other set to well-developed areas. The universities selected from the backward areas were Kohat University of Science and Technology (KUST) Kohat, University of Malakand (UoM), Shaheed Benazir Bhutto University (SBBU), Sheringal University (SU) and Khushal Khan Khattak University (KKKU), Karak and the universities selected from developed areas were National University of Modern Languages, (NUML) Islamabad, International Islamic University (IIU), Islamabad, University of Sargodha (UoS) and Gomal University(GU), Dera Ismail Khan. The study used Corder (1975)’s Error Analysis approach for analysing the errors. The study used mixed-method research design. The sample included a total of 200 students, out of which 25 students were selected from each university through simple random sampling technique. Test and interviews were used as instruments for data collection. For the identification of punctuation errors, the students were made to take a punctuation test. A probe was made into the possible reasons behind the punctuation errors by interviewing the students. The data collected was analysed by using content analysis technique. The study revealed that the most frequent errors were errors related to comma, apostrophe, and capitalization. The analysis of the interviews showed that the lack of practice on punctuation marks, lack of teaching punctuation within context, lack of checking of punctuation errors and lack of error corrective feedback on the punctuation errors were the major reasons behind the differences in the frequency of punctuation errors.

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