Discrete choice experiments are not conjoint analysis

We briefly review and discuss traditional conjoint analysis (CA) and discrete choice experiments (DCEs), widely used stated preference elicitation methods in several disciplines. We pay particular attention to the origins and basis of CA, and show that it is generally inconsistent with economic demand theory, and is subject to several logical inconsistencies that make it unsuitable for use in applied economics, particularly welfare and policy assessment. We contrast this with DCEs that have a long-standing, well-tested theoretical basis in random utility theory, and we show why and how DCEs are more general and consistent with economic demand theory. Perhaps the major message, though, is that many studies that claim to be doing conjoint analysis are really doing DCE

Archetypal analysis: a new way to segment markets based on extreme individuals

Segmenting consumers into groups has long been used to gain marketing insights (e.g., Frank, Massey & Wind 1972). Many ways to identify segments have been proposed (e.g., Kaufman & Rousseeuw 1990), although most share some common features, such as choosing representative local centered “objects ” according to some criterion. The rationale for focusing on extreme individuals in segmenting markets was noted by Allenby and Glinter (1995), who argued such consumers can be important in new product introduction and switching contexts. We discuss and illustrate a new approach called “archetypal analysis ” (AA) based on distance from “important extreme objects. ” AA has considerable potential for use in marketing, which we illustrate with two examples: 1) identifying segments from responses to attitudinal statements and 2) identifying segments from responses to discrete choice experiments. Introduction to Archetypal Analysis Archetypal analysis is a statistical technique proposed by Cutler and Breiman (1994). Cutler and Breiman note similarities and differences of AA compared with cluster centers and the concept of principal points (See Flurry 1990). Use of AA in the hard sciences is growing; fo

Overcoming challenges and improvements in best-worst elicitation: Determining what matters to Japanese wheat millers

Knowing how to produce what types of wheat with what characteristics and in what quantities is a key challenge for producer countries like Australia to successfully export wheat to various markets that consume it. Both producers and consumers would benefit by better matching what is produced to what the market(s) prefer and are willing to pay to have produced. Analysis of decision-maker choices is difficult as there are only a small number of millers in any one country that make buying decisions. Moreover, the buyers tend to use an extensive list of quality characteristics to inform their purchases. This research provides details of some of the insights that have been gained into this decision making context using best-worst scaling (BWS), as a choice-based measurement and modelling approach. The survey instrument was administered using CAPI in personal interviews with Japanese flour millers. A small number of flour millers in Japan supply the entire government regulated market with products like Udon and Ramen noodles. Face-to-face interviews were conducted with 14 individuals from four different companies that account for about 74 per cent of wheat flour production in Japan. These individuals play various roles in wheat buying, production, distribution and marketing, such as production managers, quality control specialists and new product and scientific development managers. Based on the literature and pilot discussions with wheat buyers, a list was compiled of 31 factors (attributes) that could be considered by the individuals who influence wheat buying decisions. These included technical attributes (e.g., viscograph peak height; farinograph dough stability, etc) as well as attributes common in most business-to-business trade settings that are often cited as important in many agricultural trade contexts (e.g., price; country of origin; uniformity of shipment, etc)

A1C as a Diagnostic Criteria for Diabetes in Low- and Middle-Income Settings: Evidence from Peru

OBJECTIVES: To determine the prevalence of type 2 diabetes mellitus, in three groups of Peruvian adults, using fasting glucose and glycosylated hemoglobin (A1C). METHODOLOGY/PRINCIPAL FINDINGS: This study included adults from the PERU MIGRANT Study who had fasted ≥ 8 h. Fasting glucose ≥ 126 mg/dL and A1C ≥ 6.5% were used, separately, to define diabetes. Subjects with a current diagnosis of diabetes were excluded. 964 of 988 subjects were included in this analysis. Overall, 0.9% (95%CI 0.3-1.5) and 3.5% (95%CI 2.4-4.7) had diabetes using fasting glucose and A1C criteria, respectively. Compared to those classified as having diabetes using fasting glucose, newly classified subjects with diabetes using A1C (n = 25), were older, poorer, thinner and more likely to come from rural areas. Of these, 40% (10/25) had impaired fasting glucose (IFG). CONCLUSIONS: This study shows that the use of A1C as diagnostic criteria for type 2 diabetes mellitus identifies people of different characteristics than fasting glucose. In the PERU MIGRANT population using A1C to define diabetes tripled the prevalence; the increase was more marked among poorer and rural populations. More than half the newly diagnosed people with diabetes using A1C had normal fasting glucose

Foreign body granuloma in the anterior abdominal wall mimicking an acute appendicular lump and induced by a translocated copper-T intrauterine contraceptive device: a case report

<p>Abstract</p> <p>Introduction</p> <p>Intrauterine contraceptive devices may at times perforate and migrate to adjacent organs. Such uterine perforation usually passes unnoticed with development of potentially serious complications.</p> <p>Case presentation</p> <p>A 25-year-old woman of North Indian origin presented with an acute tender lump in the right iliac fossa. The lump was initially thought to be an appendicular lump and treated conservatively. Resolution of the lump was incomplete. On exploratory laparotomy, a hard suspicious mass was found in the anterior abdominal wall of the right iliac fossa. Wide excision and bisection of the mass revealed a copper-T embedded inside. Examination of the uterus did not show any evidence of perforation. The next day, the patient gave a history of past copper-T Intrauterine contraceptive device insertion.</p> <p>Conclusions</p> <p>Copper-T insertion is one of the simplest contraceptive methods but its neglect with inadequate follow-up may lead to uterine perforation and extra-uterine migration. Regular self-examination for the "threads" supplemented with abdominal X-ray and/or ultrasound in the follow-up may detect copper-T migration early. To the best of our knowledge, this is the first report of intrauterine contraceptive device migration to the anterior abdominal wall of the right iliac fossa.</p

Error correction in bimanual coordination benefits from bilateral muscle activity: evidence from kinesthetic tracking

Although previous studies indicated that the stability properties of interlimb coordination largely result from the integrated timing of efferent signals to both limbs, they also depend on afference-based interactions. In the present study, we examined contributions of afference-based error corrections to rhythmic bimanual coordination using a kinesthetic tracking task. Furthermore, since we found in previous research that subjects activated their muscles in the tracked (motor-driven) arm, we examined the functional significance of this activation to gain more insight into the processes underlying this phenomenon. To these aims, twelve subjects coordinated active movements of the right hand with motor-driven oscillatory movements of the left hand in two coordinative patterns: in-phase (relative phase 0°) and antiphase (relative phase 180°). They were either instructed to activate the muscles in the motor-driven arm as if moving along with the motor (active condition), or to keep these muscles as relaxed as possible (relaxed condition). We found that error corrections were more effective in in-phase than in antiphase coordination, resulting in more adequate adjustments of cycle durations to compensate for timing errors detected at the start of each cycle. In addition, error corrections were generally more pronounced in the active than in the relaxed condition. This activity-related difference was attributed to the associated bilateral neural control signals (as estimated using electromyography), which provided an additional reference (in terms of expected sensory consequences) for afference-based error corrections. An intimate relation was revealed between the (integrated) motor commands to both limbs and the processing of afferent feedback

Species Differentiation on a Dynamic Landscape: Shifts in Metapopulation Genetic Structure Using the Chronology of the Hawaiian Archipelago

Species formation during adaptive radiation often occurs in the context of a changing environment. The establishment and arrangement of populations, in space and time, sets up ecological and genetic processes that dictate the rate and pattern of differentiation. Here, we focus on how a dynamic habitat can affect genetic structure, and ultimately, differentiation among populations. We make use of the chronology and geographical history provided by the Hawaiian archipelago to examine the initial stages of population establishment and genetic divergence. We use data from a set of 6 spider lineages that differ in habitat affinities, some preferring low elevation habitats with a longer history of connection, others being more specialized for high elevation and/or wet forest, some with more general habitat affinities. We show that habitat preferences associated with lineages are important in ecological and genetic structuring. Lineages that have more restricted habitat preferences are subject to repeated episodes of isolation and fragmentation as a result of lava flows and vegetation succession. The initial dynamic set up by the landscape translates over time into discrete lineages. Further work is needed to understand how genetic changes interact with a changing set of ecological interactions amongst a shifting mosaic of landscapes to achieve species formation