Hypotheses in Marketing Science: Literature Review and Publication Audit

We examined three approaches to research in marketing: exploratory hypotheses, dominant hypothesis, and competing hypotheses. Our review of empirical studies on scientific methodology suggests that the use of a single dominant hypothesis lacks objectivity relative to the use of exploratory and competing hypotheses approaches. We then conducted a publication audit of over 1,700 empirical papers in six leading marketing journals during 1984-1999. Of these, 74% used the dominant hypothesis approach, while 13 % used multiple competing hypotheses, and 13% were exploratory. Competing hypotheses were more commonly used for studying methods (25%) than models (17%) and phenomena (7%). Changes in the approach to hypotheses since 1984 have been modest; there was a slight decrease in the percentage of competing hypotheses to 11%, which is plained primarily by an increasing proportion of papers on phenomena. Of the studies based on hypothesis testing, only 11 % described the conditions under which the hypotheses would apply, and dominant hypotheses were below competing hypotheses in this regard. Marketing scientists differed substantially in their opinions about what types of studies should be published and what was published. On average, they did not think dominant hypotheses should be used as often as they were, and they underestimated their use

Analysis and Synthesis of the Dynamic Response of Retinal Neurons

theory of linear systems analysis is developed in a form directly applicable to the treatment of the Limulus retina. The dynamics of the retina may conveniently be characterized by means of a spatiotemporal transfer function, which summarizes the response of the system to moving sinusoidal gratings ( analysis ). The response of the retina to an arbitrary stimulus may then be calculated by addition of the response to suitably weighted sinusoidal stimuli ( synthesis ). Responses were obtained from the in-situ retina by means of extracellular recording of impulse activity in single optic nerve fibers. Test ommatidia were chosen in the interior of the retina, to avoid asymmetries introduced by the edge of the retina. Stimuli which varied in both space and time were produced under computer control on the screen of a display oscilloscope, and were conveyed to the Limulus eye by means of a fiber-optic taper. Transfer functions were measured using counterphase modulation of cosine gratings according to a sum-of-sinusoids temporal signal, a procedure equivalent to the use of moving gratings, for ommatidia with symmetrical receptive fields. By means of these transfer functions, the responses of the Limulus eye to visual stimuli moving at various velocities were predicted in a parameter-free Fourier synthesis calculation. There was good agreement between these predictions and the measured responses to these stimuli. A quantitative model for the dynamic, integrative action of the Limulus retina is developed, based on the original formulation for the steady state given by the Hartline- Ratliff equations. The model comprises an excitatory generator potential, and dynamic processes of self and lateral inhibition. An explicit expression for the spatiotemporal transfer function is obtained in terms of transfer functions for the generator potential, self-inhibitory, and lateral-inhibitory transductions, and spatial transforms of the lateral inhibitory kernel and the point-spread characteristic of the experimental and physiological optics. Explicit functional forms for these component transductions are adopted. The parameters which occur in these expressions serve to incorporate information about the subcellular physiology of retinal neurons into the quantitative description of the function of the retina as a whole. Procedures are described for the estimation of these parameters from empirical transfer function data. Transfer functions calculated from the model on the basis of parameters obtained with these procedures show good agreement with the corresponding empirical transfer functions. The parameter values obtained in this way are, in general, quite consistent with the results of many more direct (and frequently more invasive) measurements reported in the literature. In particular, the inhibitory kernel, as determined from our transfer function measurements, shows a small crater in the vicinity of the test-ommatidium. The dynamical model can be used to describe the response of the retina in the vicinity of its boundary, as well as in the interior. An analysis, based on the Wiener-Hopf technique, is given for the response of peripheral retinal neurons. The predictions derived from this theory were compared with experiment through the use of illumination patterns in which one half of the retina was kept in darkness, while the remaining half was presented with a moving stimulus. This procedure permitted the calibration of model transfer functions by means of methods appropriate only for interior ommatidia, while simulating the neural environment at the edge of a homogeneous retina. Significant differences between the responses to stimuli which moved toward and away from the simulated edge were observed experimentally, in good agreement with the predictions of the theory. Similar behavior was also observed at the actual anatomical boundary of the eye

Effects of portfolio planning methods on decision making: experimental results

Subjects (n = 1015) working individually in the role of managers were asked to choose between investment opportunities that would either double their investment or cause the loss of half of it. Six administrators ran experiments on 27 occasions in six countries over a five-year period. Information about the BCG matrix increased the subjects\u27 likelihood of selecting the project that was clearly less profitable. Of subjects exposed to the BCG matrix, 64% selected the unprofitable investment. Of subjects who used the BCG matrix in their analysis, 87% selected the less profitable investment

Portfolio Planning Methods: Faulty Approach or Faulty Research? A Rejoinder to Making Better Decisions by Wensley

Wensley (1994) makes three key points. First, it is worthwhile to conduct empirical studies of the value of management techniques. Second, managers probably misuse portfolio methods. Third, the Armstrong and Brodie study is flawed. We agree with all three points

Forecasting for Marketing

Research on forecasting is extensive and includes many studies that have tested alternative methods in order to determine which ones are most effective. We review this evidence in order to provide guidelines for forecasting for marketing. The coverage includes intentions, Delphi, role playing, conjoint analysis, judgmental bootstrapping, analogies, extrapolation, rule-based forecasting, expert systems, and econometric methods. We discuss research about which methods are most appropriate to forecast market size, actions of decision makers, market share, sales, and financial outcomes. In general, there is a need for statistical methods that incorporate the manager\u27s domain knowledge. This includes rule-based forecasting, expert systems, and econometric methods. We describe how to choose a forecasting method and provide guidelines for the effective use of forecasts including such procedures as scenarios

A University Deep Space CubeSat Mission: Lessons Learned from the University of Colorado Boulder Earth Escape Explorer (CU-E3)

The University of Colorado Boulder Earth Escape Explorer (CU-E3) CubeSat is a student designed and built CubeSat initially slated for launch into deep space on Artemis-1, the inaugural launch of the NASA Space Launch System (SLS). CU-E3 was designed to compete in the Cube Quest Challenge’s (CQC) Deep Space Derby for monetary prizes associated with deep space communication system performance, while also serving as a technology demonstration platform for a series of innovative university CubeSat technologies and practices, including a low-cost X-band CubeSat transmitter, an X-band reflectarray antenna, and the use of solar radiation pressure to control reaction wheel momentum build-up. An overview of the CU-E3 project, including mission concept of operations, system architecture, and major component descriptions are provided. Emphasis is focused the challenges and lessons learned as a participant of the CQC with a student designed and built deep space CubeSat. These challenges include student turnover, limited commercial ground station capabilities and availability, deep space thermal environment, secondary payload safety procedures for the human space rated SLS, and deep space trajectory variance

Loss of synchronized retinal phagocytosis and age-related blindness in mice lacking alphavbeta5 integrin.

Daily phagocytosis by the retinal pigment epithelium (RPE) of spent photoreceptor outer segment fragments is critical for vision. In the retina, early morning circadian photoreceptor rod shedding precedes synchronized uptake of shed photoreceptor particles by RPE cells. In vitro, RPE cells use the integrin receptor alphavbeta5 for particle binding. Here, we tested RPE phagocytosis and retinal function in beta5 integrin--deficient mice, which specifically lack alphavbeta5 receptors. Retinal photoresponses severely declined with age in beta5-/- mice, whose RPE accumulated autofluorescent storage bodies that are hallmarks of human retinal aging and disease. beta5-/- RPE in culture failed to take up isolated photoreceptor particles. beta5-/- RPE in vivo retained basal uptake levels but lacked the burst of phagocytic activity that followed circadian photoreceptor shedding in wild-type RPE. Rhythmic activation of focal adhesion and Mer tyrosine kinases that mediate wild-type retinal phagocytosis was also completely absent in beta5-/- retina. These results demonstrate an essential role for alphavbeta5 integrin receptors and their downstream signaling pathways in synchronizing retinal phagocytosis. Furthermore, they identify the beta5-/- integrin mouse strain as a new animal model of age-related retinal dysfunction

Forecasting Methods for Marketing: Review of Empirical Research

This paper reviews the empirical research on forecasting in marketing. In addition, it presents results from some small scale surveys. We offer a framework for discussing forecasts in the area of marketing,and then review the literature in light of that framework. Particular emphasis is given to a pragmatic interpretation of the literature and findings. Suggestions are made on what research is needed

Blood flow analysis of the aortic arch using computational fluid dynamics in a coupled 3D-0D framework

Regions of the aortic arch affected by an aneurysm or dissection may require surgical intervention using vascular grafts, which includes a means of reperfusing the supra-aortic branch vessels, comprised of the left subclavian artery (LSA), left common carotid artery (LCCA) and brachiocephalic artery. Open surgical grafts are widely used in arch reconstruction yet the graft configuration which ensures optimal post-surgical perfusion is currently poorly understood. For example, peripheral organ ischaemia and post-operative malperfusion remain a concern. It is clear, therefore, that enhanced understanding of perfusion in patient-specific cases is critical to improving clinical practice and patient outcome