نتایج جستجو برای: imputation
تعداد نتایج: 16711 فیلتر نتایج به سال:
Imputation is one of the most common methods to reduce item non_response effects. Imputation results in a complete data set, and then it is possible to use naϊve estimators. After using most of common imputation methods, mean and total (imputation estimators) are still unbiased. However their variances (imputation variances) are underestimated by naϊve variance estimators. Sampling mechanism an...
Introduction: The aim of this study was to impute missing data and to compare the effect of different doses of vitamin D supplementation on insulin resistance during pregnancy. Methods: A clinical trial study was done on 104 women with diabetes and gestational age less than 12 weeks between 1391 and...
Imputation as a method of creating low-density chips to high-density chips has been introduced to increase the accuracy of genomic selection in animals. In the current study, to investing imputation accuracy, three populations of mixed (scenario 1), pure (scenario 2) and mixed + pure (scenario 3) were simulated using QMSim. Two methods of imputation including Beagle and Flmpute were used fo...
The objective of this study was to evaluate the imputation accuracy of parent-offspring trios under different scenarios. By using simulated datasets, the performance Bayesian LASSO in genomic prediction was also examined. The genome consisted of 5 chromosomes and each chromosome was set as 1 Morgan length. The number of SNPs per chromosome was 10000. One hundred QTLs were randomly distributed a...
Genotype imputation from low-density to high-density (SNP) chips is an important step before applying genomic selection, because denser chips can provide more reliable genomic predictions. In the current research, the accuracy of genotype imputation from low and moderate-density panels (5K and 50K) to high-density panels in the purebred and crossbred populations was assessed. The simulated popu...
in this study, effect of two genotype imputation strategies, relatedness between reference panel and test populations and minor allele frequency on imputation error rate were examined with using a stochastic simulated population. reference panel and test populations were composed of 1,000 and 500 individuals, respectively. individuals in the reference panel were genotyped with using a high and ...
Background and Objectives: A major challenge that affects the longitudinal studies is the problem of missing data. Missing in the data may result in the loss of part of the information which reduces the accuracy of the estimator and obtain the results will be biased and inaccurate. Therefore, it is necessary to evaluate the missing data mechanism from a longitudinal research and to consider thi...
Background Policy makers need models to be able to detect groups at high risk of HIV infection. Incomplete records and dirty data are frequently seen in national data sets. Presence of missing data challenges the practice of model development. Several studies suggested that performance of imputation methods is acceptable when missing rate is moderate. One of the issues which was of less concern...
the relation between single nucleotide polymorphisms (snps) and some diseases has been concerned by many researchers. also the missing snps are quite common in genetic association studies. hence, this article investigates the relation between existing snps in dnmt1 of human chromosome 19 with colorectal cancer. this article aims is to presents an imputation method for missing snps not at random...
Genomic selection is a promising challenge for discovering genetic variants influencing quantitative and threshold traits for improving the genetic gain and accuracy of genomic prediction in animal breeding. Since a proportion of genotypes are generally uncalled, therefore, prediction of genomic accuracy requires imputation of missing genotypes. The objectives of this study were (1) to quantify...
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