Reproducibility in the absence of selective reporting : An illustration from large-scale brain asymmetry research

Altres ajuts: Max Planck Society (Germany).The problem of poor reproducibility of scientific findings has received much attention over recent years, in a variety of fields including psychology and neuroscience. The problem has been partly attributed to publication bias and unwanted practices such as p-hacking. Low statistical power in individual studies is also understood to be an important factor. In a recent multisite collaborative study, we mapped brain anatomical left-right asymmetries for regional measures of surface area and cortical thickness, in 99 MRI datasets from around the world, for a total of over 17,000 participants. In the present study, we revisited these hemispheric effects from the perspective of reproducibility. Within each dataset, we considered that an effect had been reproduced when it matched the meta-analytic effect from the 98 other datasets, in terms of effect direction and significance threshold. In this sense, the results within each dataset were viewed as coming from separate studies in an "ideal publishing environment," that is, free from selective reporting and p hacking. We found an average reproducibility rate of 63.2% (SD = 22.9%, min = 22.2%, max = 97.0%). As expected, reproducibility was higher for larger effects and in larger datasets. Reproducibility was not obviously related to the age of participants, scanner field strength, FreeSurfer software version, cortical regional measurement reliability, or regional size. These findings constitute an empirical illustration of reproducibility in the absence of publication bias or p hacking, when assessing realistic biological effects in heterogeneous neuroscience data, and given typically-used sample sizes

By-Passing of Terminal Market Facilities in Agricultural Marketing

The idea of centralized marketing in agrtculture has 'Usually meant that products moved from the farms. to the market facilities in a few large cities, Here in the so-called "terminal" market title and physical possession would · pass from the farmer to wholesalers and processors. Aiding in this process was the host of-middlemen, brokers, ,jobbers, receivers, commission men, wholesalers, etc ... and the many facilitating organizations.such as auction companies, stockyards, boards of trade and other organtza.tions operating the necessary display and warehousing apace. Over the past several years increasing amounts of agricultural products have been moving from the farms to processors and wholesalers without utilizing the services of the terminal personnel and facilities. Or to phrase it more accurately, ma.rketing has become more decentralized. This 1;.endency to by ... pass termina.J.. facilities will be discussed under three ma.jor headings : ( 1) The extent of the decentral:tzation, ( 2) why such a trend has developed, and (3) current and future problems due to decentralization

Collective Marketing Arrangements for Geographically Differentiated Agricultural Products: Welfare Impacts and Policy Implications

We examine the incentives of atomistic producers to differentiate and collectively market products. We analyze market and welfare effects of alternative producer organizations, discuss circumstances under which they will evolve, and describe implications for the ongoing debate between the EU and the United States. As fixed costs of development and marketing increase and the anticipated market size falls, it becomes essential to increase the producer organization's ability to control supply to cover the fixed costs associated with the introduction of differentiated products. Counterintuitively, stronger property right protection for producer organizations may enhance welfare even after a differentiated product has been developed. Copyright 2007, Oxford University Press.