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The impact of financial histories on individuals and societies: A replication of and extension of Berg el al. (1995)
We replicate and extend the social history treatment of the Berg, Dickhaut, and McCabe (1995) investment game, to further document how the reporting of financial history influences how laboratory societies organize themselves over time. We replicate Berg et al. (1995) by conducting a No History and a Financial History session to determine whether a report summarizing the financial transactions of a previous experimental session will significantly reduce entropy in the amounts sent by Investors and returned by Stewards in the investment game, as Berg et al. (1995) found. We extend Berg et al. (1995) in two ways. First, we conduct a total of five sessions (one No History and four Financial History sessions). Second, we introduce Shannon's (1948) measure of entropy from information theory to assess whether the introduction of financial transaction history reduces the amount of dispersion in the amounts invested and returned across generations of players. Results across sessions indicate that entropy declined in both the amounts sent by Investors and the percentage returned by Stewards, but these patterns are weaker and mixed compared to those in the Berg et al. (1995) study. Additional research is needed to test how initial conditions, path dependencies, actors' strategic reasoning about others' behavior, multiple sessions, and communication may mediate the impact of financial history. The study's multiple successive Financial History sessions and entropy measure are new to the investment game literature
Effect of Statistical Fluctuation in Monte Carlo Based Photon Beam Dose Calculation on Gamma Index Evaluation
The gamma-index test has been commonly adopted to quantify the degree of
agreement between a reference dose distribution and an evaluation dose
distribution. Monte Carlo (MC) simulation has been widely used for the
radiotherapy dose calculation for both clinical and research purposes. The goal
of this work is to investigate both theoretically and experimentally the impact
of the MC statistical fluctuation on the gamma-index test when the fluctuation
exists in the reference, the evaluation, or both dose distributions. To the
first order approximation, we theoretically demonstrated in a simplified model
that the statistical fluctuation tends to overestimate gamma-index values when
existing in the reference dose distribution and underestimate gamma-index
values when existing in the evaluation dose distribution given the original
gamma-index is relatively large for the statistical fluctuation. Our numerical
experiments using clinical photon radiation therapy cases have shown that 1)
when performing a gamma-index test between an MC reference dose and a non-MC
evaluation dose, the average gamma-index is overestimated and the passing rate
decreases with the increase of the noise level in the reference dose; 2) when
performing a gamma-index test between a non-MC reference dose and an MC
evaluation dose, the average gamma-index is underestimated when they are within
the clinically relevant range and the passing rate increases with the increase
of the noise level in the evaluation dose; 3) when performing a gamma-index
test between an MC reference dose and an MC evaluation dose, the passing rate
is overestimated due to the noise in the evaluation dose and underestimated due
to the noise in the reference dose. We conclude that the gamma-index test
should be used with caution when comparing dose distributions computed with
Monte Carlo simulation
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