scholarly journals The effect of continued selection of phenotypic intermediates on gene frequency

1964 ◽  
Vol 5 (3) ◽  
pp. 341-353 ◽  
Author(s):  
R. N. Curnow
Keyword(s):  
Gene Frequency ◽  
Selection Procedure ◽  
High Variability ◽  
Considerable Importance ◽  
Selection Procedures ◽  
Population Mean ◽  
Section 8 ◽  
Selection Of

The selection of animals or plants for high values of a certain character may favour not only genotypes associated with these high values but also genotypes associated with high variability. Any differences between genotypes in variability may therefore be of considerable importance in plant and livestock improvement programmes as well as in evolution. The effects of various selection procedures on variability have been studied in three recent experiments [Falconer & Robertson (1956) Falconer (1957) and Prout (1962)]. In these experiments one line was continued by selecting, in each generation, parents with values of a particular character near the population mean. Manning (1955, 1956) has described the effects of this kind of selection applied to cotton. Robertson (1956) derived and discussed the theory of such selection procedures when certain simplifying approximations can be made We shall obtain some more general results and show that Robertson was incorrect in saying that the selection procedure would lead to gene fixation even if the heterozygotes are less variable than the homozygotes. The importance of the results is discussed in section 8.

scholarly journals 'n psigometriese oudit op ‘n bestaande keuringsprosedure

2002 ◽  
Vol 28 (3) ◽  
Author(s):  
E. Cross ◽  
W. Marais ◽  
H. Steel ◽  
C. C. Theron
Keyword(s):  
Selection Procedure ◽  
Developmental History ◽  
Selection Procedures ◽  
Ideal Approach ◽  
History Of ◽  
Selection Of

The validity and credibility of assertions on the efficiency and equity of selection procedures is dependent on the methodology with which the procedure was developed and justified. An ideal approach to the development and justification of a selection procedure was derived from standard guidelines and operationalized in the form of a comprehensive checklist. A psychometric audit on the developmental history of the selection procedure for the selection of commission advisors was undertaken. Various shortcomings were identified and rectified or recommendations were made on rectifying them. The audit found that the selection procedure had zero validity, negative utility and discriminated unfairly. Opsomming Die geldigheid en geloofwaardigheid van uitsprake oor die effektiwiteit en billikheid van ‘n keuringsprosedure is ‘n funksie van die metodologie waarmee die prosedure ontwikkel en regverdig is. ‘n Ideale benadering tot die ontwikkeling en regverdiging van ‘n keuringsprosedure is uit standaard riglyne afgelei en geoperasionaliseer in die vorm van ‘n omvattende kontrolelys. ‘n Psigometriese oudit is onderneem op die ontwikkelingsgeskiedenis van ‘n keuringsprosedure vir die keuring van kommissie-adviseurs. Verskeie tekortkominge is geïdentifiseer en reggestel of aanbevelings ten opsigte van regstelling is gemaak. Die oudit het bevind dat die keuringsprosedure oor zero geldigheid beskik, negatiewe nutwaarde toon en onbillik diskrimineer.

Comparison of Model Selection Method Using Data from Classical Designed Experiment

2013 ◽  
Vol 677 ◽  
pp. 357-362
Author(s):  
Natthasurang Yasungnoen ◽  
Patchanok Srisuradetchai
Keyword(s):  
Model Selection ◽  
Quantitative Research ◽  
Selection Procedure ◽  
Information Criterion ◽  
P Value ◽  
Selection Procedures ◽  
Final Model ◽  
Designed Experiment ◽  
Using Data ◽  
Selection Of

Model selection procedures play important role in many researches especially quantitative research. . In several area of sciences, the analysis and model selection of experiments are often used and often contains two fundamental goals associated with the experimental response of interest which are to determine the best model. The way to address these goals is to implement a model selection procedure. Then, the objectives of this research are to determine whether or not the final models selected are in agreement or differ substantially across the three approaches to model selection: using Akaike’s Information Criterion, using a p-value criterion, and using a stepwise procedure.. Generally, results from these three models are usually compare to each other. All selected models are based on the heredity principle to design the possible model for each design. The actual data from literature, consisting of the 2x3 and 32 and 3x4 factorial designs are used to determine the final model. The results show that the P-Value WH and Stepwise methods give the highest percentage of matched model.

scholarly journals PROCEDURA KONKURSOWEGO DOBORU KADR KIEROWNICZYCh. PROBLEMATYKA PRAWNA

2016 ◽  
Vol 12 (3) ◽  
pp. 79
Author(s):  
Tomasz Duraj
Keyword(s):  
Significant Influence ◽  
Selection Procedure ◽  
Legal Issues ◽  
Legal Regulations ◽  
Legal Analysis ◽  
Selection Procedures ◽  
Competitive Selection ◽  
The Subject ◽  
Management Staff ◽  
Selection Of

THE COMPETITIVE SELECTION PROCEDURE FOR MANAGEMENT STAFF: LEGAL ISSUES Summary This analysis relates to the legal issues in the competitive selection of management staff. Under the current provisions in Poland many legal acts pertain to this issue, giving an inhomogeneous set of regulations for the principles of conducting such procedures in particular domains of public, social and economic affairs. The subject of this article is a detailed description of the stages of the procedure for the competitive selection of management staff. Good legislation to regulate the selection procedures for competitions for management appointments will have a significant influence on the effectiveness of the adopted method of selection. The author presents the successive stages of the procedures for such competitions and conducts an in-depth legal analysis, paying specific attention to legal doubts arising in connection with the application of the current law. On the basis of his analysis he formulates some proposals de lege ferenda addressed to the legislator on the introduction of requisite amendments and supplements to the legal regulations for the procedure of competitive selection of management staff.

Improvement of olfactometric measurement accuracy and repeatability by optimization of panel selection procedures

2010 ◽  
Vol 61 (5) ◽  
pp. 1267-1278 ◽  
Author(s):  
L. Capelli ◽  
S. Sironi ◽  
R. Del Rosso ◽  
P. Céntola ◽  
S. Bonati
Keyword(s):  
Degrees Of Freedom ◽  
Selection Procedure ◽  
Selection Procedures ◽  
Accuracy And Precision ◽  
Repeated Analysis ◽  
The Right ◽  
Accuracy And Repeatability ◽  
Selection Of ◽  
Dynamic Olfactometry

The EN 13725:2003, which standardizes the determination of odour concentration by dynamic olfactometry, fixes the limits for panel selection in terms of individual threshold towards a reference gas (n-butanol in nitrogen) and of standard deviation of the responses. Nonetheless, laboratories have some degrees of freedom in developing their own procedures for panel selection and evaluation. Most Italian olfactometric laboratories use a similar procedure for panel selection, based on the repeated analysis of samples of n-butanol at a concentration of 60 ppm. The first part of this study demonstrates that this procedure may originate a sort of “smartening” of the assessors, which means that they become able to guess the right answers in order to maintain their qualification as panel members, independently from their real olfactory perception. For this reason, the panel selection procedure has been revised with the aim of making it less repetitive, therefore preventing the possibility for panel members to be able to guess the best answers in order to comply with the selection criteria. The selection of new panel members and the screening of the active ones according to this revised procedure proved this new procedure to be more selective than the “standard” one. Finally, the results of the tests with n-butanol conducted after the introduction of the revised procedure for panel selection and regular verification showed an effective improvement of the laboratory measurement performances in terms of accuracy and precision.

How to obtain valid tests and confidence intervals after propensity score variable selection?

2019 ◽  
Vol 29 (3) ◽  
pp. 677-694 ◽  
Author(s):  
Oliver Dukes ◽  
Stijn Vansteelandt
Keyword(s):  
Propensity Score ◽  
Variable Selection ◽  
Confidence Intervals ◽  
Selection Procedure ◽  
Routine Practice ◽  
Finite Sample ◽  
Major Drawback ◽  
Sample Distribution ◽  
Selection Procedures ◽  
Selection Of

The problem of how to best select variables for confounding adjustment forms one of the key challenges in the evaluation of exposure or treatment effects in observational studies. Routine practice is often based on stepwise selection procedures that use hypothesis testing, change-in-estimate assessments or the lasso, which have all been criticised for – amongst other things – not giving sufficient priority to the selection of confounders. This has prompted vigorous recent activity in developing procedures that prioritise the selection of confounders, while preventing the selection of so-called instrumental variables that are associated with exposure, but not outcome (after adjustment for the exposure). A major drawback of all these procedures is that there is no finite sample size at which they are guaranteed to deliver treatment effect estimators and associated confidence intervals with adequate performance. This is the result of the estimator jumping back and forth between different selected models, and standard confidence intervals ignoring the resulting model selection uncertainty. In this paper, we will develop insight into this by evaluating the finite-sample distribution of the exposure effect estimator in linear regression, under a number of the aforementioned confounder selection procedures. We will show that by making clever use of propensity scores, a simple and generic solution is obtained in the context of generalized linear models, which overcomes this concern (under weaker conditions than competing proposals). Specifically, we propose to use separate regularized regressions for the outcome and propensity score models in order to construct a doubly robust ‘g-estimator’; when these models are sufficiently sparse and correctly specified, standard confidence intervals for the g-estimator implicitly incorporate the uncertainty induced by the variable selection procedure.

Judicial Merit Selection: Beliefs about Fairness and the Undermining of Gender Diversity on the Bench

2020 ◽  
pp. 106591292097171
Author(s):  
Nancy B. Arrington
Keyword(s):  
Experimental Evidence ◽  
Institutional Design ◽  
A Priori ◽  
Gender Diversity ◽  
Selection Procedure ◽  
Procedural Fairness ◽  
Unintended Consequences ◽  
Selection Procedures ◽  
Judicial Selection ◽  
Selection Of

Much attention is paid to how mechanisms for selecting political officials shape which types of officials hold positions of power, but selection procedures do not always produce the desired outcomes. In the context of the judiciary, many expected “merit” selection procedures to facilitate the selection of women justices to the bench, an expectation that has not been realized. Applying theories of procedural fairness to judicial selection procedures, I argue that observers’ beliefs that merit selection procedures are more “fair” (relative to unilateral selection procedures) makes observers more accepting of all-male benches. Survey experimental evidence demonstrates that respondents do perceive merit selection procedures as more fair than gubernatorial selection procedures, a priori. In turn, respondents are less critical of all-male courts when judges are selected through a merit selection procedure. These findings contribute to our understanding of the ways in which (1) selection institutions shape prospects for gender diversity, (2) institutional design can have unintended consequences, and (3) procedural fairness can obscure accountabilituy for suboptimal outcomes.

Identifying Measurement Invariant Item Sets in Cross-Cultural Settings Using an Automated Item Selection Procedure

Methodology ◽  
2018 ◽  
Vol 14 (4) ◽  
pp. 177-188 ◽  
Author(s):  
Martin Schultze ◽  
Michael Eid
Keyword(s):  
Measurement Invariance ◽  
Optimal Solution ◽  
Selection Procedure ◽  
Cross Cultural ◽  
Item Selection ◽  
Ant System ◽  
Item Quality ◽  
Ant System Algorithm ◽  
Selection For ◽  
Selection Of

Abstract. In the construction of scales intended for the use in cross-cultural studies, the selection of items needs to be guided not only by traditional criteria of item quality, but has to take information about the measurement invariance of the scale into account. We present an approach to automated item selection which depicts the process as a combinatorial optimization problem and aims at finding a scale which fulfils predefined target criteria – such as measurement invariance across cultures. The search for an optimal solution is performed using an adaptation of the [Formula: see text] Ant System algorithm. The approach is illustrated using an application to item selection for a personality scale assuming measurement invariance across multiple countries.

Combination of ribosome and phage display for fast selection of high affinity VHH antibody fragments

2019 ◽  
pp. 27-33
Author(s):  
YuE Kravchenko ◽  
SV Ivanov ◽  
DS Kravchenko ◽  
EI Frolova ◽  
SP Chumakov
Keyword(s):  
Phage Display ◽  
Selection Procedure ◽  
Free System ◽  
Phage Displays ◽  
High Affinity ◽  
Binding Domains ◽  
A Cell ◽  
Vhh Antibodies ◽  
Efficiency Of Selection ◽  
Selection Of

Selection of antibodies using phage display involves the preliminary cloning of the repertoire of sequences encoding antigen-binding domains into phagemid, which is considered the bottleneck of the method, limiting the resulting diversity of libraries and leading to the loss of poorly represented variants before the start of the selection procedure. Selection in cell-free conditions using a ribosomal display is devoid from this drawback, however is highly sensitive to PCR artifacts and the RNase contamination. The aim of the study was to test the efficiency of a combination of both methods, including pre-selection in a cell-free system to enrich the source library, followed by cloning and final selection using phage display. This approach may eliminate the shortcomings of each method and increase the efficiency of selection. For selection, alpaca VHH antibody sequences suitable for building an immune library were used due to the lack of VL domains. Analysis of immune libraries from the genes of the VH3, VHH3 and VH4 families showed that the VHH antibodies share in the VH3 and VH4 gene groups is insignificant, and selection from the combined library is less effective than from the VHH3 family of sequences. We found that the combination of ribosomal and phage displays leads to a higher enrichment of high-affinity fragments and avoids the loss of the original diversity during cloning. The combined method allowed us to obtain a greater number of different high-affinity sequences, and all the tested VHH fragments were able to specifically recognize the target, including the total protein extracts of cell cultures.

scholarly journals Gradient boosting for linear mixed models

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Colin Griesbach ◽  
Benjamin Säfken ◽  
Elisabeth Waldmann
Keyword(s):  
Random Effects ◽  
Mixed Models ◽  
Selection Procedure ◽  
Classification Theory ◽  
Gradient Boosting ◽  
Random Structure ◽  
Boosting Algorithm ◽  
The One ◽  
Biased Estimates ◽  
Selection Of

Abstract Gradient boosting from the field of statistical learning is widely known as a powerful framework for estimation and selection of predictor effects in various regression models by adapting concepts from classification theory. Current boosting approaches also offer methods accounting for random effects and thus enable prediction of mixed models for longitudinal and clustered data. However, these approaches include several flaws resulting in unbalanced effect selection with falsely induced shrinkage and a low convergence rate on the one hand and biased estimates of the random effects on the other hand. We therefore propose a new boosting algorithm which explicitly accounts for the random structure by excluding it from the selection procedure, properly correcting the random effects estimates and in addition providing likelihood-based estimation of the random effects variance structure. The new algorithm offers an organic and unbiased fitting approach, which is shown via simulations and data examples.

scholarly journals A comparison of two methods for predicting changes in the distribution of gene frequency when selection is applied repeatedly to a finite population

1969 ◽  
Vol 13 (2) ◽  
pp. 117-126 ◽  
Author(s):  
Derek J. Pike
Keyword(s):  
Iterative Procedure ◽  
Gene Frequency ◽  
Finite Population ◽  
Transition Matrices ◽  
Single Cycle ◽  
Gene Frequencies ◽  
Mean And Variance ◽  
The Mean ◽  
The One ◽  
Selection Of

Robertson (1960) used probability transition matrices to estimate changes in gene frequency when sampling and selection are applied to a finite population. Curnow & Baker (1968) used Kojima's (1961) approximate formulae for the mean and variance of the change in gene frequency from a single cycle of selection applied to a finite population to develop an iterative procedure for studying the effects of repeated cycles of selection and regeneration. To do this they assumed a beta distribution for the unfixed gene frequencies at each generation.These two methods are discussed and a result used in Kojima's paper is proved. A number of sets of calculations are carried out using both methods and the results are compared to assess the accuracy of Curnow & Baker's method in relation to Robertson's approach.It is found that the one real fault in the Curnow-Baker method is its tendency to fix too high a proportion of the genes, particularly when the initial gene frequency is near to a fixation point. This fault is largely overcome when more individuals are selected. For selection of eight or more individuals the Curnow-Baker method is very accurate and appreciably faster than the transition matrix method.

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