The average laboratory samples a population of 7,300 Amazon Mechanical Turk workers

Using capture-recapture analysis we estimate the effective size of the active Amazon Mechanical Turk (MTurk) population that a typical laboratory can access to be about 7,300 workers. We also estimate that the time taken for half of the workers to leave the MTurk pool and be replaced is about 7 months. Each laboratory has its own population pool which overlaps, often extensively, with the hundreds of other laboratories using MTurk. Our estimate is based on a sample of 114,460 completed sessions from 33,408 unique participants and 689 sessions across seven laboratories in the US, Europe, and Australia from January 2012 to March 2015

The role of information search and its influence on risk preferences

According to the ‘Description–Experience gap’ (DE gap), when people are provided with the descriptions of risky prospects they make choices as if they overweight the probability of rare events; but when making decisions from experience after exploring the prospects’ properties, they behave as if they underweight such probability. This study revisits this discrepancy while focusing on information-search in decisions from experience. We report findings from a lab-experiment with three treatments: a standard version of decisions from description and two versions of decisions from experience: with and without a ‘history table’ recording previously sampled events. We find that people sample more from lotteries with rarer events. The history table proved influential; in its absence search is more responsive to cues such as a lottery’s variance while in its presence the cue that stands out is the table’s maximum capacity. Our analysis of risky choices captures a significant DE gap which is mitigated by the presence of the history table. We elicit probability weighting functions at the individual level and report that subjects overweight rare events in experience but less so than in description. Finally, we report a measure that allows us to compare the type of DE gap found in studies using choice patterns with that inferred through valuation and find that the phenomenon is similar but not identical across the two methods

Of Black Swans and Tossed Coins: Is the Description-Experience Gap in Risky Choice Limited to Rare Events?

When faced with risky decisions, people tend to be risk averse for gains and risk seeking for losses (the reflection effect). Studies examining this risk-sensitive decision making, however, typically ask people directly what they would do in hypothetical choice scenarios. A recent flurry of studies has shown that when these risky decisions include rare outcomes, people make different choices for explicitly described probabilities than for experienced probabilistic outcomes. Specifically, rare outcomes are overweighted when described and underweighted when experienced. In two experiments, we examined risk-sensitive decision making when the risky option had two equally probable (50%) outcomes. For experience-based decisions, there was a reversal of the reflection effect with greater risk seeking for gains than for losses, as compared to description-based decisions. This fundamental difference in experienced and described choices cannot be explained by the weighting of rare events and suggests a separate subjective utility curve for experience

The Average Laboratory Samples a Population of 7,300 Amazon Mechanical Turk Workers.

Using capture-recapture analysis we estimate the effective size of the active Amazon Mechanical Turk (MTurk) population that a typical laboratory can access to be about 7,300 workers. We also estimate that the time taken for half of the workers to leave the MTurk pool and be replaced is about 7 months. Each laboratory has its own population pool which overlaps, often extensively, with the hundreds of other laboratories using MTurk. Our estimate is based on a sample of 114,460 completed sessions from 33,408 unique participants and 689 sessions across seven laboratories in the US, Europe, and Australia from January 2012 to March 2015

Data for The average laboratory samples a population of 7,300 Amazon Mechanical Turk workers 2012-2017

Using capture-recapture analysis we estimate the effective size of the active Amazon Mechanical Turk (MTurk) population that a typical laboratory can access to be about 7,300 workers. We also estimate that the time taken for half of the workers to leave the MTurk pool and be replaced is about 7 months. Each laboratory has its own population pool which overlaps, often extensively, with the hundreds of other laboratories using MTurk. Our estimate is based on a sample of 114,460 completed sessions from 33,408 unique participants and 689 sessions across seven laboratories in the US, Europe, and Australia from January 2012 to March 2015

Alcaparrosaite, K 3

Alcaparrosaite, ideally K3Ti4+Fe3+(SO4)4O(H2O)2, is a new mineral from the Alcaparrosa mine, Cerritos Bayos, El Loa Province, Antofagasta, Chile (IMA2011-024). The mineral occurs on and intergrown with coquimbite, and is also associated with ferrinatrite, krausite, pertlikite, pyrite, tamarugite and voltaite. It is a relatively early phase which forms during the oxidation of pyritic masses under increasingly arid conditions. Alcaparrosaite crystallizes from hyperacidic solutions in a chemical environment that is consistent with its association with coquimbite. It occurs as pale yellow blades and tapering prisms up to 4 mm in length, flattened on {010} and elongated along [100]. The observed crystal forms are {010}, {110}, {1.13.0} and {021}. The mineral is transparent and has a white streak, vitreous lustre, Mohs hardness of about 4, brittle tenacity, conchoidal fracture and no cleavage. The measured and calculated densities are 2.80(3) and 2.807 g cm_3, respectively. It is optically biaxial (+) with a = 1.643(1), b = 1.655(1), g = 1.680(1) (white light), 2Vmeas = 70(2)º and 2Vcalc = 70.3º. The mineral exhibits strong parallel dispersion, r 4sF), Ti4+ and Fe3+, in roughly equal amounts, occupy the same octahedrally coordinated site. Octahedra are linked into dimers by corner sharing. The SO4 tetrahedra link the dimers into chains parallel to [001] and link the chains into undulating sheets parallel to {010}. The sheets link via 10- and 11-coordinated K atoms in the interlayer region. The structure shares some features with that of goldichite