SU-GG-I-156: Potential Sources of Variation in Quantitative Ultrasound Quality Control Measurements

2008 ◽  
Vol 35 (6Part5) ◽  
pp. 2677-2677
Author(s):  
R Marsh ◽  
R Stafford ◽  
D Reeve
Keyword(s):  
Quality Control ◽  
Quantitative Ultrasound ◽  
Potential Sources ◽  
Sources Of Variation

scholarly journals Fiber tractography bundle segmentation depends on scanner effects, acquisition, diffusion sensitization, and bundle segmentation workflow

2021 ◽  
Author(s):  
Kurt Schilling ◽  
Chantal M.W. Tax ◽  
Francois Rheault ◽  
Colin B Hansen ◽  
Qi Yang ◽  
...  
Keyword(s):  
White Matter ◽  
Mean Diffusivity ◽  
B Value ◽  
Fiber Tractography ◽  
Acquisition Protocol ◽  
Segmentation Methods ◽  
Combining Data ◽  
Potential Sources ◽  
Sources Of Variation ◽  
The Brain

When investigating connectivity and microstructure of white matter pathways of the brain using diffusion tractography bundle segmentation, it is important to understand potential confounds and sources of variation in the process. While cross-scanner and cross-protocol effects on diffusion microstructure measures are well described (in particular fractional anisotropy and mean diffusivity), it is unknown how potential sources of variation effect bundle segmentation results, which features of the bundle are most affected, where variability occurs, nor how these sources of variation depend upon the method used to reconstruct and segment bundles. In this study, we investigate four potential sources of variation, or confounds, for bundle segmentation: variation (1) across scan repeats, (2) across scanners, (3) across acquisition protocol, and (4) across diffusion sensitization. We employ four different bundle segmentation workflows on two benchmark multi-subject cross-scanner and cross-protocol databases, and investigate reproducibility and biases in volume overlap, shape geometry features of fiber pathways, and microstructure features within the pathways. We find that the effects of acquisition protocol, in particular acquisition resolution, result in the lowest reproducibility of tractography and largest variation of features, followed by scanner-effects, and finally b-value effects which had similar reproducibility as scan-rescan variation. However, confounds varied both across pathways and across segmentation workflows, with some bundle segmentation workflows more (or less) robust to sources of variation. Despite variability, bundle dissection is consistently able to recover the same location of pathways in the deep white matter, with variation at the gray matter/ white matter interface. Next, we show that differences due to the choice of bundle segmentation workflows are larger than any other studied confound, with low-to-moderate overlap of the same intended pathway when segmented using different methods. Finally, quantifying microstructure features within a pathway, we show that tractography adds variability over-and-above that which exists due to noise, scanner effects, and acquisition effects. Overall, these confounds need to be considered when harmonizing diffusion datasets, interpreting or combining data across sites, and when attempting to understand the successes and limitations of different methodologies in the design and development of new tractography or bundle segmentation methods.

Precarious Manhood Predicts Support for Aggressive Policies and Politicians

2020 ◽  
pp. 014616722096357
Author(s):  
Sarah H. DiMuccio ◽  
Eric D. Knowles
Keyword(s):  
Death Penalty ◽  
Real World ◽  
Signal Strength ◽  
Congressional Elections ◽  
Electoral Behavior ◽  
Election Study ◽  
Search Terms ◽  
Potential Sources ◽  
Sources Of Variation ◽  
The Relationship

Precarious manhood (PM) theory posits that males are expected to actively maintain their reputations as “real men.” We propose that men’s concern about failing to meet masculine standards leads them to embrace policies and politicians that signal strength and toughness—or what we term political aggression. Three correlational studies support this claim. In Study 1, men’s fear of failing to meet masculine expectations predicted their support for aggressive policies (e.g., the death penalty), but not policies lacking aggressive features (e.g., affirmative action). Studies 2 and 3 utilized Google searches to assess the relationship between regional levels of PM and real-world electoral behavior. The use of search terms related to masculine anxieties correlated with Donald Trump’s vote share in the 2016 general election (Study 2) and, confirming preregistered predictions, with Republican candidates’ vote shares in 2018 congressional elections (Study 3). We close by discussing potential sources of variation in PM.

scholarly journals Section 4: Investigation of Potential Sources of Variation

Radiocarbon ◽  
2003 ◽  
Vol 45 (2) ◽  
pp. 175-212 ◽  
Keyword(s):  
Statistical Analysis ◽  
Limited Information ◽  
Potential Sources ◽  
Sources Of Variation ◽  
Background Material ◽  
Laboratory Procedures ◽  
Different Levels ◽  
Modern Standard

The design of FIRI is such that for each laboratory, we have some basic, though limited, information on the laboratory procedures, including the method of pretreatment applied to the samples, the modern standard, and the background material used. These can be considered as factors in the experiment and through statistical analysis, we can investigate whether they offer a statistically significant explanation of the observed variation. The different levels of the factors are described in Table 4.1. In addition, the laboratory type is also considered as a further factor (with 3 levels of LSC, GPC, and AMS).

Testing hypotheses concerning the formation of shell growth marks in marine pelecypods

1991 ◽  
Vol 69 (3) ◽  
pp. 535-546 ◽  
Author(s):  
Edwin Bourget ◽  
Hélène Bérard ◽  
Vibeke Brock
Keyword(s):  
Shell Growth ◽  
Growth Accounting ◽  
Short Term ◽  
Tidal Period ◽  
Growth Increments ◽  
Potential Sources ◽  
Sources Of Variation ◽  
Shell Deposition ◽  
The Individual ◽  
External Growth

This paper reviews the evidence supporting the current hypotheses (daily, tidal, endogenous, and other rhythms of growth) accounting for short-term periodicity in the formation of marks (external growth ridges and internal growth increments) on the shell of marine pelecypod molluscs. With few exceptions our analysis shows too much unexplained variability and the availability of too few studies of potential sources of variation for the proposed cycles of mark formation (circadian, circatidal) to be accepted. Since shell deposition takes the form of marks, which must be discrete in frequency (0, 1, or 2 per given day or tidal period), we submit that individual frequencies must be used to test hypotheses concerning the rhythms of shell growth mark formation, and we propose the use of three criteria: (i) that departure of the individual measured frequency from the expected frequency should not be more than the maximal error in measurements (maximal counting errors made by the observer); (ii) should condition one be violated, then the so-called "missing" or "superfluous" marks should be clearly accounted for; (iii) that potential sources of variation (e.g., age, habitat, locality, season) should not significantly influence the frequency of formation of the marks.

A model-based meta-analysis for estimating species-specific wood density and identifying potential sources of variation

2013 ◽  
Vol 102 (1) ◽  
pp. 194-208 ◽  
Author(s):  
Kiona Ogle ◽  
Sharmila Pathikonda ◽  
Karla Sartor ◽  
Jeremy W. Lichstein ◽  
Jeanne L. D. Osnas ◽  
...  
Keyword(s):  
Wood Density ◽  
Meta Analysis ◽  
Model Based ◽  
Potential Sources ◽  
Sources Of Variation ◽  
Species Specific

Analysis of potential sources of variation in tissue culture derived celery plants

1994 ◽  
Vol 124 (2) ◽  
pp. 383-398 ◽  
Author(s):  
ANNE DONOVAN ◽  
HAMISH A COLLIN ◽  
SUSAN ISAAC ◽  
A MARTIN MORTIMER
Keyword(s):  
Tissue Culture ◽  
Potential Sources ◽  
Sources Of Variation

MEASUREMENT OF PLASMA RENIN-SUBSTRATE IN MAN

1973 ◽  
Vol 56 (2) ◽  
pp. 159A-171 ◽  
Author(s):  
MALCOLM TREE
Keyword(s):  
Angiotensin Ii ◽  
Substrate Concentration ◽  
Plasma Renin ◽  
Angiotensin I ◽  
Renin Substrate ◽  
Potential Sources ◽  
Sources Of Variation ◽  
Method Of Measurement ◽  
Inhibitor Solution

SUMMARY Values of plasma renin-substrate concentration in man vary widely according to the method of measurement used. Potential sources of variation have been tested and, as far as possible, excluded in the method described here. Blood was diluted rapidly in an angiotensinase-inhibitor solution containing EDTA and phenanthroline; plasma was separated by centrifugation and the renin-substrate in the specimen was hydrolysed by renin to angiotensin I which was identified as such by chromatography and radioimmunoassay. Angiotensin I was used as a standard to determine the amount of angiotensin formed on incubation. Use of angiotensin II for a standard, as in other methods, led to falsely low values of plasma renin-substrate concentration. Recovery of added substrate was 94%. Changes of plasma renin-substrate concentration in some physiological and pathological states are reported briefly.

scholarly journals Addressing potential sources of variation in several non-destructive techniques for measuring firmness in apples

2009 ◽  
Vol 104 (1) ◽  
pp. 33-46 ◽  
Author(s):  
D. Molina-Delgado ◽  
S. Alegre ◽  
P. Barreiro ◽  
C. Valero ◽  
M. Ruiz-Altisent ◽  
...  
Keyword(s):  
Potential Sources ◽  
Sources Of Variation ◽  
Non Destructive ◽  
Non Destructive Techniques

The Reliability of Framework for Teaching Scores in Kindergarten

2020 ◽  
Vol 38 (7) ◽  
pp. 831-845
Author(s):  
Helen Patrick ◽  
Brian F. French ◽  
Panayota Mantzicopoulos
Keyword(s):  
Teacher Evaluation ◽  
Classroom Environment ◽  
Generalizability Theory ◽  
Observation Instrument ◽  
Reliability Estimates ◽  
Potential Sources ◽  
Sources Of Variation ◽  
Framework For Teaching ◽  
And Mathematics ◽  
Reading And Mathematics

We evaluated the score stability of the Framework for Teaching (FFT), a prominent observation instrument used for teacher evaluation. Three raters each scored 200 reading and mathematics lessons taught by 20 kindergarten teachers. Using Generalizability theory analyses, we decomposed the FFT’s Classroom Environment, Instruction, and Total scores into potential sources of variation (teachers, lessons, raters, and their interactions). The scores’ variances attributable to differences among teachers were 71% and 76% for Classroom Environment, 49% and 37% for Instruction, and 69% and 66% for the Total score, for reading and mathematics, respectively. Reliability estimates (G) ranged from 0.92 to 0.96 for Classroom Environment and Total scores; they were 0.87 and 0.79 for reading and mathematics Instruction. Decision studies indicated that two raters, each scoring three reading lessons or four mathematics lessons, are necessary to achieve sufficiently reliable Total scores. For Instruction scores, three raters each scoring seven readings lessons are needed; more than four raters each scoring eight lessons are needed for mathematics.

What Causes Variation in Functional Response Parameters?

2021 ◽  
pp. 27-46
Author(s):  
John P. DeLong
Keyword(s):  
Empirical Evidence ◽  
Functional Response ◽  
Phenotypic Traits ◽  
Potential Sources ◽  
Sources Of Variation ◽  
And Behaviors ◽  
The Way

The parameters of the functional response are not traits. They represent processes such as hunting and digesting prey. Thus, all the traits that influence the way predators and prey encounter each other in space and the morphologies and behaviors that influence capture, evasion, or digestion are all potential sources of variation in the functional response parameters. In this chapter, I cover how we break the parameters down mathematically so that the connection between the parameters and traits is more transparent. I review the empirical evidence for the dependence of functional response parameters on phenotypic traits, temperature, and habitats, and I showcase some examples of these effects.

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