An asymptotic analysis of the logrank test

Asymptotic expansions for the null distribution of the logrank statistic and its distribution under local proportional hazards alternatives are developed in the case of iid observations. The results, which are derived from the work of Gu (1992) and Taniguchi (1992), are easy to interpret, and provide some theoretical justification for many behavioral characteristics of the logrank test that have been previously observed in simulation studies. We focus primarily upon (i) the inadequacy of the usual normal approximation under treatment group imbalance; and, (ii) the effects of treatment group imbalance on power and sample size calculations. A simple transformation of the logrank statistic is also derived based on results in Konishi (1991) and is found to substantially improve the standard normal approximation to its distribution under the null hypothesis of no survival difference when there is treatment group imbalance.     

Design and analysis for survival data under order restrictions with a modified logrank test

We previously proposed a class of ordered weighted logrank tests for analysing censored survival data under order restrictions. However, the power of these tests is asymmetrical with respect to possible alternative configurations. While it is superior in most cases, the power can be inferior to the non-ordered logrank test in extreme cases. We propose a modified ordered logrank test which performs uniformly better than the non-ordered test. The power of the modified test is equivalent to the generalized Jonckheere's test but its computation is much simpler. We give sample size requirements for sufficient power to reject the global null hypothesis at specified hazard ratios between the control group and the best group. Following Fisher's least significant difference (LSD) strategy for multiple comparisons, power investigations indicate that the nominal power for the global test carries over to the control versus best comparison during pairwise testing. The power for detecting intermediate survival differences is inadequate but the sample sizes required to detect such differences may be impractical in most applications.     

Familiar interacting object pairs are perceptually grouped.

Identification of objects in a scene may be influenced by functional relations among those objects. In this study, observers indicated whether a target object matched a label. Each target was presented with a distractor object, and these were sometimes arranged to interact (as if being used together) and sometimes not to interact. When the distractor was semantically related to the label, identification was more accurate for targets arranged to interact with that distractor. This effect depended on observers' ability to perceptually integrate the stimulus objects, suggesting that it was perceptual in nature. The effect was not attributable to attentional cuing and did not depend on expectation of certain object pairs. These data suggest that familiar functional groupings of objects are perceptually grouped. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential radiation diagnosis of microcalcinates grouped in breast

A complex methods was used to examine 39 females with the microcalcinates grouped in the breast. The diagnostic efficiency of a number of mammographic and sonographic signs was comparatively evaluated. Ultrasonography was shown to be advisable in differentially diagnosing cancer and sclerosing adenosis. A combination of mammography and sonography may establish an accurate diagnosis in 78% of cases.     

Using hierarchical linear modeling to analyze grouped data.

This article discusses how to use a random coefficient modeling technique known as hierarchical linear modeling to analyze data collected within groups. The article describes how to use this technique to examine group- and individual-level phenomena, including examination of how individual-level relationships vary as a function of group characteristics. A comparison of hierarchical linear modeling with more traditional, ordinary-least-squares techniques and a presentation of how to implement analyses to test specific hypotheses are included. Included are brief discussions of pertinent issues such as the impact of different centering options, the analysis of categorical variables, distinctions between random and fixed effects, and balanced and unbalanced designs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A second-generation interactive classroom television system for the partially sighted

This paper describes the various parts of a new interactive classroom television system (ICTS) that is being used by partially sighted elementary school children. This ICTS permits children to view one of seven separately controlled TV screens and thereby be in continuous visual communication with their teacher, classmates, and classroom. Comments are made on the advantages of educating partially sighted children separately from normally sighted children.     

A phonomecanographic test of hyperthyroidism

Systolic intervals may be studied by phonomechanography. This provides data regarding the function of the left ventricle. In the absence of any problem of intraventricular conduction or valvular lesion, such information is particularly valuable. Thyroxine impregnation, whetHer active directly and/or by catecholamine hypersecretion, results in cardiac hyperkinesia which is reflected not only by tachycardia but also a shortening penetration time and contraction of the ventricular muscle. This shows itself within systole as a change in the relation between the duration of the pre-ejection phase (PPE) and the ejection phase. The first decreases whilst the second remains normal and their ratio changes, PPE/E changes from a normal value of 0.34 +/- 0.04 to 0.25 +/- 0.03. These tests are not only of value in diagnosis but also make it possible to observe the effects of treatment. It is certain that a true phonomechanographic syndrome of cardiac hyperkinesia may be described. The commonest, though not the only, aetiology is hyperthyroidism.     

A better sheet formability test

A new test for sheet metal formability was designed, constructed, and used to evaluate several coated and uncoated sheet materials. Results from the OSU Formability Test were also compared with standard limiting dome height (LDH) tests and with finite element simulations. These results show that the new test is more reproducible, even using relatively uncontrolled equipment, more closely follows the desirable plane-strain path, and takes roughly one fifth of the time to perform relative to LDH. Moreover, there is good correlation between formability evaluated using the two tests. Strain measurements and finite element simulations revealed that the improvements are a result of the new test geometry, which produces more stable and repeatable plane-strain states near the fracture location. Formerly Graduate Research Assistant, The Ohio State University Formerly Postdoctoral Researcher, The Ohio State University     

One-at-a-time versus grouped presentation of mug book pictures: Some surprising results.

Eyewitnesses to a simulated crime attempted to identify the perpetrator from a computerized mug book. The 208 mug book pictures were presented either 1 mug shot per page or in groups of 12 mug shots per page. Half of the mug books were arranged by similarity to the perpetrator as determined by a facial recognition algorithm, and half were randomly arranged. In contrast to past findings with photospreads, false-positive identifications were significantly higher using the one-at-a-time procedure than the grouped procedure. Results suggest that the best practice for mug books may be the use of groups of pictures per page rather than the one-at-a-time procedure long advocated by experts for use in lineups and photospreads. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Anterior release test. A new test for occult shoulder instability

Occult shoulder instability is recognized as a significant contributor to shoulder dysfunction in throwing athletes. Diagnosis of occult instability by physical examination remains challenging. The anterior release test is a test for physical examination of the shoulder. It was developed to facilitate detection of occult anterior instability. One hundred shoulders were examined preoperatively by the same examiner. Based on surgical findings, the shoulders were classified as anterior instability or other. The results of examination were compared with the operative findings. Sensitivity was calculated as 91.9%, specificity 88.9%, positive predictive value 87.1%, negative predictive value 93.0%, and accuracy 90.2%. The anterior release test is a reliable and reproducible test for the detection of the unstable shoulder.     

Overexpression of rice phytochrome A partially complements phytochrome B deficiency in Arabidopsis

The red/far-red reversible phytochromes play a central role in regulating the development of plants in relation to their light environment. Studies on the roles of different members of the phytochrome family have mainly focused on light-labile, phytochrome A and light-stable, phytochrome B. Although these two phytochromes often regulate identical responses, they appear to have discrete photosensory functions. Thus, phytochrome A predominantly mediates responses to prolonged far-red light, as well as acting in a non-red/far-red-reversible manner in controlling responses to light pulses. In contrast, phytochrome B mediates responses to prolonged red light and acts photoreversibly under light-pulse conditions. However, it has been reported that rice (Oryza sativa L.) phytochrome A operates in a classical red/far-red reversible fashion following its expression in transgenic tobacco plants. Thus, it was of interest to determine whether transgenic rice phytochrome A could substitute for loss of phytochrome B in phyB mutants of Arabidopsis thaliana (L.) Heynh. We have observed that ectopic expression of rice phytochrome A can correct the reduced sensitivity of phyB hypocotyls to red light and restore their response to end-of-day far-red treatments. The latter is widely regarded as a hallmark of phytochrome B action. However, although transgenic rice phytochrome A can correct other aspects of elongation growth in the phyB mutant it does not restore other responses to end-of-day far-red treatments nor does it restore responses to low red:far-red ratio. Furthermore, transgenic rice phytochrome A does not correct the early-flowering phenotype of phyB seedlings.     

A model of automatic attention attraction when mapping is partially consistent.

A model is described to account for the data of Durso, Cooke, Breen, and Schvaneveldt (1987). On the basis of the relative frequency of an item's presentation as a target, the item develops an automatic tendency to attract attention. When stimuli are then displayed, each calls the attention system to a degree determined by its present strength. We assume that attention eventually drifts to the strongest stimulus (which is then given as a response), but in a time determined inversely by the difference in strength between the two strongest stimuli. A version of this model in which the strengths were freely estimated parameters predicted the various elements of the data with good accuracy. In other versions of the model, strength values were derived from assumptions concerning the learning of automatism. Two of these models, quite different in character, captured the major qualitative features of the data. Further empirical tests of the models are suggested. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relations of test item characteristics to test preparation/test practice effects: A quantitative summary.

Examined 10 studies on the effects of test preparation or test practice to provide information relevant to the strategy of developing tests that do not exhibit significant susceptibility to test preparation. Only studies that reported effects by individual item type and used aptitude tests for post-secondary admissions or employment were included in the analysis. The item-level effects were related to a number of test item characteristics, including item format, difficulty level, and complexity of test directions. Strong relations were noted between test preparation and/or practice effects and (a) the length and complexity of test directions and (b) the item format used. The number of words used to convey directions seemed to be a significant aspect of the complexity, as did the fixed-format nature of many of the most susceptible item types. It is suggested that only studies conducted at the level of individual item types are likely to yield results that will help test developers construct relatively "uncoachable" tests. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A simple test device for electrometers

Electrometers used in dosimetric instruments need to be checked regularly in order to measure and maintain the prescribed dose to the patient. This paper describes the function of a simple but accurate test device for electrometers. A number of electrometers have been tested and compared with calibrations performed by the Swedish Standard Dosimetry Laboratory (SSDL). The device can be used to test current, resistance, voltage and charge measurements. The charge can be conducted to the electrometer in different ways, and the input resistance of the electrometer can also be determined. The calibration factors obtained by the device are in good agreement with results obtained from calibrations at the SSDL.     

A test of behavioral rigidity.

A battery of rigidity tests, some of which were selected from the literature and others which were newly constructed were administered to a group of 216 Ss selected to represent a wide range of age, occupation, and education. Factor analysis of the results resulted in the rejection of the hypothesis of a single rigidity factor. Instead, behavioral rigidity seems best described by three factors, interpreted as "motor-cognitive speed," "personality-perceptual rigidity," and "motor-cognitive rigidity." Subsequent testing on another population produced a simple structure matrix in substantial agreement with that obtained from the first sample. Norms and test manual are made available through the American Documentation Institute. (PsycINFO Database Record (c) 2010 APA, all rights reserved)