Choosing between Parametric and Non-parametric Tests

A common question in comparing two sets of measurements is whether to use a parametric testing procedure or a non-parametric procedure. The question is even more important in dealing with smaller samples. Here, using simulation, several parametric and nonparametric tests, such as, t-test, Normal test, Wilcoxon Rank Sum test, van-der Waerden Score test, and Exponential Score test are compared

STEM Outreach Activities to Inspire Future Engineers and Scientists

With some basic tools and a plan, students can discover the exciting world engineering and science. We will provide inexpensive materials (paper, masking tape, etc.) for a hands-on activity with professional engineers who appreciate the various skills of budding engineers interested in coming into the field

The Geometric Maximum Traveling Salesman Problem

We consider the traveling salesman problem when the cities are points in R^d for some fixed d and distances are computed according to geometric distances, determined by some norm. We show that for any polyhedral norm, the problem of finding a tour of maximum length can be solved in polynomial time. If arithmetic operations are assumed to take unit time, our algorithms run in time O(n^{f-2} log n), where f is the number of facets of the polyhedron determining the polyhedral norm. Thus for example we have O(n^2 log n) algorithms for the cases of points in the plane under the Rectilinear and Sup norms. This is in contrast to the fact that finding a minimum length tour in each case is NP-hard. Our approach can be extended to the more general case of quasi-norms with not necessarily symmetric unit ball, where we get a complexity of O(n^{2f-2} log n). For the special case of two-dimensional metrics with f=4 (which includes the Rectilinear and Sup norms), we present a simple algorithm with O(n) running time. The algorithm does not use any indirect addressing, so its running time remains valid even in comparison based models in which sorting requires Omega(n \log n) time. The basic mechanism of the algorithm provides some intuition on why polyhedral norms allow fast algorithms. Complementing the results on simplicity for polyhedral norms, we prove that for the case of Euclidean distances in R^d for d>2, the Maximum TSP is NP-hard. This sheds new light on the well-studied difficulties of Euclidean distances.Comment: 24 pages, 6 figures; revised to appear in Journal of the ACM. (clarified some minor points, fixed typos

Failure of Harmonic Gears During Verification of a Two-Axis Gimbal for the Mars Reconnaissance Orbiter Spacecraft

The Mars Reconnaissance Orbiter (MRO) spacecraft has three two-axis gimbal assemblies that support and move the High Gain Antenna and two solar array wings. The gimbal assemblies are required to move almost continuously throughout the mission's seven-year lifetime, requiring a large number of output revolutions for each actuator in the gimbal assemblies. The actuator for each of the six axes consists of a two-phase brushless dc motor with a direct drive to the wave generator of a size-32 cup-type harmonic gear. During life testing of an actuator assembly, the harmonic gear teeth failed completely, leaving the size-32 harmonic gear with a maximum output torque capability less than 10% of its design capability. The investigation that followed the failure revealed limitations of the heritage material choices that were made for the harmonic gear components that had passed similar life requirements on several previous programs. Additionally, the methods used to increase the stiffness of a standard harmonic gear component set, while accepted practice for harmonic gears, is limited in its range. The stiffness of harmonic gear assemblies can be increased up to a maximum stiffness point that, if exceeded, compromises the reliability of the gear components for long life applications

Stability, delivery and functions of human sperm RNAs at fertilization

Increasing attention has focused on the significance of RNA in sperm, in light of its contribution to the birth and long-term health of a child, role in sperm function and diagnostic potential. As the composition of sperm RNA is in flux, assigning specific roles to individual RNAs presents a significant challenge. For the first time RNA-seq was used to characterize the population of coding and non-coding transcripts in human sperm. Examining RNA representation as a function of multiple methods of library preparation revealed unique features indicative of very specific and stage-dependent maturation and regulation of sperm RNA, illuminating their various transitional roles. Correlation of sperm transcript abundance with epigenetic marks suggested roles for these elements in the pre- and post-fertilization genome. Several classes of non-coding RNAs including lncRNAs, CARs, pri-miRNAs, novel elements and mRNAs have been identified which, based on factors including relative abundance, integrity in sperm, available knockout data of embryonic effect and presence or absence in the unfertilized human oocyte, are likely to be essential male factors critical to early post-fertilization development. The diverse and unique attributes of sperm transcripts that were revealed provides the first detailed analysis of the biology and anticipated clinical significance of spermatozoal RNAs

Kidney transplant graft outcomes in 379 257 recipients on 3 continents

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/145422/1/ajt14694_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/145422/2/ajt14694.pd

Visual Field Endpoints Based on Subgroups of Points May Be Useful in Glaucoma Clinical Trials: A Study With the Humphrey Field Analyzer and Compass Perimeter

PRECIS: Visual field endpoints based on average deviation of specific subsets of points rather than all points may offer a more homogenous dataset without necessarily worsening test-retest variability and so may be useful in clinical trials. PURPOSE: To characterize outcome measures encompassing particular subsets of visual field points and compare them as obtained with Humphrey (HVF) and Compass perimeters. METHODS: 30 patients with imaging-based glaucomatous neuropathy performed a pair of 24-2 tests with each of 2 perimeters. Non-weighted mean deviation (MD) was calculated for the whole field and separate vertical hemifields, and again after censoring of points with low sensitivity (MDc) and subsequently including only "abnormal" points with total deviation probability of <5% (MDc5%) or <2% (MDc2%). Test-retest variability was assessed using Bland-Altman 95% limits of agreement (95%LoA). RESULTS: For the whole field, using HVF, MD was -7.5±6.9▒dB, MDc -3.6±2.8▒dB, MDc5% -6.4±1.7▒dB and MDc2% -7.3±1.5▒dB. With Compass MD was -7.5±6.6, MDc -2.9±1.7▒dB, MDc5% -6.3±1.5, and MDC2% -7.9±1.6. The respective 95% LoA were 5.5, 5.3, 4.6 and 5.6 with HVF, and 4.8, 3.7, 7.1 and 7.1 with Compass. The respective number of eligible points were 52, 42±12, 20±11 and 15±9 with HVF, and 52, 41.2±12.6, 10±7 and 7±5 with Compass. With both machines, standard deviation (SD) and 95%LoA increased in hemifields compared to the total field, but this increase was mitigated after censoring. CONCLUSIONS: Restricting analysis to particular subsets of points of interest in the visual field after censoring points with low sensitivity, as compared with using the familiar total field mean deviation, can provide outcome measures with a broader range of mean deviation, a markedly reduced SD and therefore more homogenous dataset, without necessarily worsening test-retest variability

Lessons for COVID-19 vaccination from eight federal government direct communication evaluations

We discuss eight randomized evaluations intended to increase vaccination uptake conducted by the US General Services Administration’s Office of Evaluation Sciences (OES). These evaluations had a median sample size of 55,000, deployed a variety of behaviorally-informed direct communications, and used administrative data to measure vaccination uptake. The confidence interval from an internal meta-analysis shows changes in vaccination rates ranging from -0.004 to 0.394 percentage points. Two studies yielded statistically significant increases, of 0.59 and 0.16 percentage points. The other six were not statistically significant, although the studies were powered to detect effect sizes in line with published research. This work highlights the likely effects of government communications and demonstrates the value of conducting rapid evaluations to support COVID-19 vaccination efforts

The Freshman, vol. 5, no. 1

The Freshman was a weekly, student newsletter issued on Mondays throughout the academic year. The newsletter included calendar notices, coverage of campus social events, lectures, and athletic teams. The intent of the publication was to create unity, a sense of community, and class spirit among first year students