A method of selecting an item response model with a genetic algorithm is proposed, where a model indicator variable is regarded as a chromosome to distinguish other individuals. This scheme enables a model for each item to be selected automatically. The genetic algorithm with the set of techniques that is implemented here is called the simple genetic algorithm, and the results obtained from simulation studies were satisfactory. An issue with the graded response model and the generalized partial credit model was examined using simulation studies and numerical examples was to find which was the more useful of these two prevailing kinds. The results obtained from simulation studies proved the graded response model fit the data more flexibly, since it fit the data generated under the generalized partial credit model more frequently than for the opposite case. However, the generalized partial credit model was more suitable for two real data sets.
This is an experimental economics research on human behaviour in “small decision making”. I set up ambiguity treatments in which there are two states of nature: a favourable state and an unfavourable state, but only one of them obtains on any given trial. The decision makers' basic task is a binary choice between a risky option with higher expected value and a riskless option with lower expected value. The one-person game is iterated hundreds of times. Experimental results are reported with several findings, such as underweighting of rare events and deviations from expected value maximisation. Finally, I investigate the imperfect Bayesian decision makers observed in the experiments by exploring to what extent they can update prior probabilities and reflect it in making decisions.
By using structural equations, we investigated the effect of chronic stress on salivary cortisol rhythm and proposed a causal model of chronic stress by using psychosocial and physiological data. First, 111 healthy workers (48 males, 63 females) completed questionnaires on chronic stress and lifestyle habits. Then, they provided saliva samples and answered questionnaires that were prepared to assess their psychological states 5 times (on waking up and at 10:00, 11:40, 14:00, and 16:00) on workdays. Structural equation modeling (SEM) revealed that chronic stress and longer commuting time resulted in sleep irregularities and this disrupted the cortisol circadian rhythm. This suggests that chronic stress disrupts the cortisol circadian rhythm even in healthy individuals, and sleep regularity mediates the effect of chronic stress on the cortisol rhythm.
In canonical correlation analysis (CCA), it is important to estimate the number of nonzero canonical correlations in the population. One way to estimate the number is to consider the dimensionality testing problem. In CCA for continuous variables, some test statistics for the problem have been derived under the normality assumption. However, there are only a few papers on test statistics in CCA for categorical variables. In this article, a test statistic in CCA for categorical variables is suggested. The test statistic is derived from the rational used for continuous variables. Some properties of the test statistic are examined through mathematical investigations and numerical simulations.