scholarly journals Testing Twin Means and Estimating Genetic Variance. Basic Methodology for the Analysis of Quantitative Twin Data

1979 ◽  
Vol 28 (1) ◽  
pp. 35-40 ◽  
Author(s):  
Joe C. Christian
Keyword(s):  
Hypothesis Testing ◽  
Genetic Variance ◽  
Twin Data ◽  
Simple Task ◽  
Twin Model ◽  
Twin Methodology

Twin methodology for the analysis of continuously distributed traits is presented as a guideline for initial steps in the analysis of twin data. Tests for heterogeneity of twin means and variances are reviewed along with estimates of genetic variance.Analysis of twin data appears on the surface to be a rather simple task, but investigators may well be confused by the wealth of choices available for hypothesis testing. This paper is designed to help the less experienced investigator, with perhaps a modest amount of data, begin analysis with maximum attention to testing all testable assumptions of the twin model, and using recent examples of applications of the methods.

scholarly journals Quality Prediction and Control of Assembly and Welding Process for Ship Group Product Based on Digital Twin

Scanning ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Lei Li ◽  
Di Liu ◽  
Jinfeng Liu ◽  
Hong-gen Zhou ◽  
Jiasheng Zhou
Keyword(s):  
Quality Control ◽  
Welding Process ◽  
Quality Prediction ◽  
Twin Data ◽  
Time Data ◽  
Digital Twin ◽  
Twin Model ◽  
Prediction And Control ◽  
And Control ◽  
Group Product

In view of the problems of lagging and poor predictability for ship assembly and welding quality control, the digital twin technology is applied to realize the quality prediction and control of ship group product. Based on the analysis of internal and external quality factors, a digital twin-based quality prediction and control process was proposed. Furthermore, the digital twin model of quality prediction and control was established, including physical assembly and welding entity, virtual assembly and welding model, the quality prediction and control system, and twin data. Next, the real-time data collection based on the Internet of Things and the twin data organization based on XML were used to create a virtual-real mapping mechanism. Then, the machine learning technology is applied to predict the process quality of ship group products. Finally, a small group is taken as an example to verify the proposed method. The results show that the established prediction model can accurately evaluate the welding angular deformation of group products and also provide a new idea for the quality control of shipbuilding.

Estimates of Genetic Variance for Anterior Fontanelle Development in the NCPP Twin Population

1980 ◽  
Vol 29 (2) ◽  
pp. 151-155 ◽  
Author(s):  
Michael Melnick ◽  
Ntinos C. Myrianthopoulos ◽  
Joe C. Christian
Keyword(s):  
Genetic Variance ◽  
Brain Growth ◽  
Anterior Fontanelle ◽  
Twin Data ◽  
Qualitative Trait ◽  
Developmental Variation ◽  
Blacks And Whites ◽  
Mean Differences ◽  
One Year ◽  
Chorion Type

There are several dynamic influences on anterior fontanelle development in infants; among them, brain growth, dural attachments, suture development, and osteogenesis. It thus seems reasonable to hypothesize that variation in anterior fontanelle development between infants, related and unrelated, might have a significant genetic component. Anterior fontanelle size was quantitated by the method of Popich and Smith for 94 monozygotic (MZ) and 187 dizygotic (DZ) four-month-old twin pairs. The general model for estimating genetic variance from quantitative twin data was applied to MZ and DZ twins and then separately by chorion type. Since there were significant mean differences between blacks and whites, races were analyzed separately. The within-pair mean square estimates of genetic variance (ĜWT) were highly significant for both blacks (P < 0.02) and whites (P < 0.002). Comparisons of means, total variances, and among-pair mean squares within races revealed no heterogeneity. There were also no significant chorion effects. Since the anterior fontanelle closes at around 1–1½ years of age, it was evaluated at age one in 95 MZ and 194 DZ twin pairs as a qualitative trait – ie, open vs closed, concordance vs discordance. There were no significant differences in proband concordance rates between MZ and DZ twin pairs for either blacks (P > 0.5) or whites (P > 0.10). Again, there were no significant chorion effects. These data suggest that anterior fontanelle developmental variation has a significant genetic variance component at four months of age but not at one year. This finding may be related to the rapid brain growth witnessed between birth and eight to nine months of age.

Transfer of Training in a Fault Diagnosis Task

1993 ◽  
Vol 37 (18) ◽  
pp. 1272-1276
Author(s):  
Charles T. Dammon ◽  
David M. Lane
Keyword(s):  
Fault Diagnosis ◽  
Hypothesis Testing ◽  
Transfer Of Training ◽  
Task Sharing ◽  
Testing Strategy ◽  
Training Task ◽  
Simple Task ◽  
Far Transfer ◽  
Surface Features ◽  
Complicated Task

Two experiments on the learning and transfer of the hypothesis testing strategy of testing easy-to-test hypotheses first were conducted. The first experiment found that this strategy could be discovered and used in a very simple fault diagnosis task but not in a slightly more complicated task. Subjects who learned the strategy in the simple task were able to transfer it to the more complicated task. The second experiment showed far transfer: The learning of this principle of hypothesis testing transferred to a task sharing no surface features with the training task. It is concluded that it is worthwhile to train people on the use of fault diagnosis strategies.

The Analysis of Marital Interaction in Cross-Sectional Twin Data

1987 ◽  
Vol 36 (1) ◽  
pp. 41-49 ◽  
Author(s):  
A.C. Heath
Keyword(s):  
Social Interaction ◽  
Genetic Variance ◽  
Environment Interaction ◽  
Marital Interaction ◽  
Twin Data ◽  
Cross Sectional ◽  
Genotype Environment Interaction ◽  
Married Individuals ◽  
Males And Females ◽  
Reciprocal Imitation

AbstractThe effects on twin data of social interaction between spouses is examined. When social interaction leads to an increase in marital resemblance (eg through reciprocal imitation), the variance of married individuals is increased, compared to the variance of unmarried individuals. Furthermore, the expected correlations between concordant married twin pairs will be lower than the expected correlations between concordant unmarried twin pairs, with the discordant twin correlations being intermediate in value. It is therefore possible, in principle, to detect the effects of marital interaction without using either longitudinal data or data on spouse pairs. However, to be detectable in twin data, marital interaction must be strong, or must exhibit marked asymmetry of effects between males and females. Genotype × environment interaction can also produce heterogeneity of correlation between concordant married, discordant, and concordant unmarried twin pairs, when genetic and environmental effects interact with marital status. However, this will usually produce increased estimates of the genetic component of variance in unmarried twins, whereas marital interaction produces increased genetic variance in married twins.

The assessment of dependence in the study of stressful life events: validation using a twin design

1999 ◽  
Vol 29 (6) ◽  
pp. 1455-1460 ◽  
Author(s):  
K. S. KENDLER ◽  
L. M. KARKOWSKI ◽  
C. A. PRESCOTT
Keyword(s):  
Life Events ◽  
Genetic Factors ◽  
Stressful Life Events ◽  
Model Fitting ◽  
Population Based ◽  
Stressful Life ◽  
Twin Design ◽  
Twin Model ◽  
Twin Methodology ◽  
Population Based Registry

Background. In the assessment of stressful life events (SLEs), researchers have often tried to evaluate whether individual events are dependent or independent of the respondent's behaviour. We sought to validate this evaluation using a twin methodology. We predicted that dependent SLEs would be more heritable than independent SLEs.Methods. We explored, by twin modelling, the resemblance in two pairs of past-year personal and network SLEs rated individually, by trained interviewers, on a four-point dependence–independence scale. We examined results from two waves of interviews with 785 female–female twin pairs ascertained from a population based registry.Results. Twin model-fitting found no evidence for genetic effects on personal or network independent SLEs. However, familial–environmental factors played an important role in the aetiology of network independent SLEs. For personal and network dependent SLEs, by contrast, three of four analyses suggested a significant aetiological role for genetic factors with estimated heritabilities ranging from 19 to 51%.Conclusions. Our results support the validity of interviewer assessments of dependence versus independence of SLEs. As predicted, these assessments were relatively successful at distinguishing SLEs that were influenced by genetic factors from those that were not.

Estimates of Genetic Variance for Some Selected Morphometric Characters: A Twin Study

1984 ◽  
Vol 33 (3) ◽  
pp. 509-514 ◽  
Author(s):  
J.C. Sharma ◽  
K. Sharma
Keyword(s):  
Twin Study ◽  
Genetic Variance ◽  
Genetic Component ◽  
Twin Data ◽  
Morphometric Traits ◽  
Morphometric Characters ◽  
Mean Values ◽  
Head Breadth ◽  
Skinfold Measurements ◽  
The Mean

AbstractResults on genetic variability in some of the morphometric characters on head and face, body girths and skin folds, based on 45 MZ and 67 like-sex DZ twin pairs, are presented. The data were subjected to a method which eliminated possible biases in the estimated genetic variances that could result from heterogeneity of total variances between zygosities of the 17 head and face measurements, heterogeneity was observed for only bizygomatic diameter. Head breadth means differed between MZ and DZ twins, indicating bias in the trait's genetic variance analysis. The results indicated a significant genetic component in these morphometric traits. For 11 girth and skinfold measurements, the t'-test based on hierarchical structure of twin data, also failed to reveal any appreciable difference between the mean values of MZ and DZ twins. Heterogeneity of total variance between zygosities was observed for three skinfold measurements, ie, biceps, triceps and suprailiac. The girth measurements, however, did not reveal any heterogeneity of total variances between the zygosities. The estimates of genetic variance revealed stronger genetic component for the girths than for the skinfolds.

The estimation of genetic variance from twin data

1970 ◽  
Vol 1 (1) ◽  
pp. 11-19 ◽  
Author(s):  
J. K. Haseman ◽  
R. C. Elston
Keyword(s):  
Genetic Variance ◽  
Twin Data

The Problem of Genotype-Environment Correlation in the Estimation of Heritability from Monozygotic and Dizygotic Twins

1976 ◽  
Vol 25 (1) ◽  
pp. 86-99 ◽  
Author(s):  
Arthur R. Jensen
Keyword(s):  
Assortative Mating ◽  
Genetic Variance ◽  
Simultaneous Equations ◽  
Twin Data ◽  
Environmental Correlation ◽  
Environmental Variance ◽  
Environmental Correlations ◽  
Quadratic Equations ◽  
Dizygotic Twins ◽  
Mz Twins

It is commonly, but incorrectly, assumed that the presence of genotype × environment covariance must necessarily reduce the heritability (h2) as estimated from twin data, when the formula used to obtain h2 makes no assumption about G × E covariance or assumes that it is zero. But, in fact, G × E covariance does not always reduce the genetic variance, and it can be shown under some conditions, an increase in the G × E covariance implies a greater genetic variance. The effect of G × E covariance on h2 as estimated from data on MZ and DZ twins, depends jointly upon the degree of assortative mating and the degree of environmental correlation between MZ twins and between DZ twins. A method, based on the solution of a pair of simultaneous quadratic equations, is proposed for estimating the range of h2 from twin data under varying assumed values for assortative mating, the environmental correlations between MZ and DZ twins, and the G × E covariance. The solution of three simultaneous equations permits direct estimation of the genetic variance, environmental variance, and G × E covariance, under varying reasonable assumed values for assortative mating and the MZ and DZ environmental correlations. Examples of the method are based on intelligence tests scores of MZ and DZ twins.

Sign in / Sign up

Export Citation Format

Share Document