Combination Of Measurement Error Research Articles

The Psychometric Properties of the Christian Nationalism Scale

AbstractA growing body of research connects Christian nationalism—a preference for a religiously conservative political regime—to social and political beliefs. This paper raises questions about the validity of a popular scale used to measure those attitudes. I begin by exploring the factor structure of the six-item Christian nationalism index. I then show how semi-supervised machine learning can be used to illustrate classification problems within that scale. Finally, I demonstrate that this index performs poorly at the interval level, a combination of measurement error and the sorting out of religious and political preferences. These attitudes have become so bound up in conventional politics that they often exhibit a threshold rather than a linear relationship to political preferences. I conclude with an appeal for care in matching theory to empirics: Christian nationalism is a prominent political theology, but research must grapple with the limitations of prevailing measurement tools when operationalizing it.

Collective Computation in Animal Fission-Fusion Dynamics.

Recent work suggests that collective computation of social structure can minimize uncertainty about the social and physical environment, facilitating adaptation. We explore these ideas by studying how fission-fusion social structure arises in spider monkey (Ateles geoffroyi) groups, exploring whether monkeys use social knowledge to collectively compute subgroup size distributions adaptive for foraging in variable environments. We assess whether individual decisions to stay in or leave subgroups are conditioned on strategies based on the presence or absence of others. We search for this evidence in a time series of subgroup membership. We find that individuals have multiple strategies, suggesting that the social knowledge of different individuals is important. These stay-leave strategies provide microscopic inputs to a stochastic model of collective computation encoded in a family of circuits. Each circuit represents an hypothesis for how collectives combine strategies to make decisions, and how these produce various subgroup size distributions. By running these circuits forward in simulation we generate new subgroup size distributions and measure how well they match food abundance in the environment using transfer entropies. We find that spider monkeys decide to stay or go using information from multiple individuals and that they can collectively compute a distribution of subgroup size that makes efficient use of ephemeral sources of nutrition. We are able to artificially tune circuits with subgroup size distributions that are a better fit to the environment than the observed. This suggests that a combination of measurement error, constraint, and adaptive lag are diminishing the power of collective computation in this system. These results are relevant for a more general understanding of the emergence of ordered states in multi-scale social systems with adaptive properties–both natural and engineered.

Performance analysis of a folding flow micromixer

The performance of a folding flow micromixer in the Stokes flow regime is investigated computationally and experimentally. Consistency with a previously derived general scaling relation is demonstrated and the geometric parameters in the scaling relation are determined for this mixer. Measured data from a second similar mixer are correctly predicted using the scaling relation, thus showing that the approach allows quantitative prediction of mixing. This paper focuses on the errors associated with such predictions. Basic errors, expressed as variations in the standard deviation of the concentration profile, were estimated to be −10% for the computation and −30% for the experiment at the highest values of Peclet number considered. It is shown that this experimental error was mostly due to depth averaging of the spectroscopic technique used for concentration measurement at the high Peclet numbers. However, extra uncertainty is associated with chip fabrication tolerances and this was investigated further. Measurements at the outlet of nine different mixer chips of notionally identical design revealed variations in mixing of ±26%. This variation was attributed to misalignment of the glass layers determining the geometry of the mixer in the chip. Thus, the combination of measurement error and misalignment means predictions of the concentration standard deviation for the mixer may get non-uniformity wrong by up to 50%. Ensuring a required uniformity, however, simply requires adding a few further elements to the mixer to allow for this uncertainty. Application of the scaling relation to mixer design is highlighted by a discussion of the options available for improving the performance of the experimental mixer.

Optimisation versus certainty: understanding the issue of heterogeneity in economic evaluation

This paper considers how the information provided by economic evaluation for decision-makers can fail to optimise use of health resources and how assessment of the relative cost-effectiveness of health care interventions can be misleading unless heterogeneity within populations is taken into account. The cost-effectiveness of an intervention is not a point estimate but an average chosen from within a distribution of different results. The normal interpretation of the distribution around that point is often mistakenly assumed to be the ‘white noise’ of measurement error. In reality this variance is a combination of measurement error and true heterogeneity of results. There remains an overemphasis on pursuing certainty which stems from the fact that the methods involved were originally devised to measure dichotomous outcomes not continuous ones such as cost-effectiveness ratios. It is argued in this paper that more consideration be given to the heterogeneous nature of costs and effects across populations in analysis and policy making.

Ultrasonic determination of single crystal sapphire fiber modulus

Single crystal α-Al2O3, (sapphire) fibers of ∼ 100 μm diameter have recently emerged as candidates for stiffening and strengthening high temperature composites. The Young's modulus of these fibers depends upon their crystallographic orientation, ranging from a high of 461 GPa for thec-orientation to a low of ∼373 GPa for orientations 45° off thec-axis. A deviation of the fibers' axial orientation from the c-axis and thus a reduction in the fibers' axial modulus can sometimes occur during the fiber growth process, and so a simple reliable method is needed to characterize the modulus and/or orientation of the fibers. A laser generated-piezoelectric transducer detected ultrasonic method has been used for this purpose. It has been found that a clear correlation exists between the velocity of the first arriving ultrasonic signal and the deviation of the fiber's axis from thec-axis. The measured velocity is found to be in reasonably good agreement with the calculated bar velocity,ν b =√E/ρ, for the fiber, providing an estimate of the fiber's orientation dependent Young's modulus. The small differences between the measured and the calculated velocities are believed to be caused by a combination of measurement errors, uncertainties in the reference elastic compliance constants of α-Al2O3 and the presence of small volume fractions of pores and other (low modulus) aluminum oxide phases in the fibers.

A RADIAL-VELOCITY STUDY OF THE NITROGEN O SUPERGIANT HD 105056.

ABSTRACT An investigation of the radial velocity of the ON supergiant HD 105056 has shown it to be variable with a small range (30-40 km/sec) and short time scale (a few days), but no satisfactory periodicity has been found in the variations. Evidence is found for a stellar wind of variable magnitude, and there are small absorption-line intensity changes in the spectrum possibly with a very short time scale (not greater than 1 hour). Either the star is not a binary and the variations arise entirely in the stellar wind; or, if it is a binary, it must have a low-mass companion and/or low inclination, and the small-amplitude velocity period is obscured by the combination of measurement errors and stellar wind effects.