The performance of dichotomous and polytomous IRT models in equating testlet-based tests was compared in this study.To clarify the conditions under which dichotomous and polytomous item response models produce differing results, the DIMTEST program was used for testing essential...

This paper provides an industry standard on how to quantify the shape of the implied volatility smirk in the equity index options market. Our local expansion method uses a second-order polynomial to describe the implied volatility-moneyness function and relates the coefficients of the polynomial...

This study investigates the relationship between consumer debt and aggregate economic activity based on time series methods and directed acyclic graphs (DAG). Quarterly US data, measured over the period 1980 to 2003, on consumer debt, gross domestic product (GDP), interest rates, housing starts,...

A theoretical model for evaluating the efficiency of concentrating PV–TE (photovoltaic–thermoelectric) hybrid system is developed in this paper. Hybrid systems with different photovoltaic cells are studied, including crystalline silicon photovoltaic cell, silicon thin-film photovoltaic cell,...

The speed-density or flow-density relationship has been considered as the foundation of traffic flow theory. Existing single-regime models calibrated by the least square method (LSM) could not fit the empirical data consistently well both in light-traffic/free-flow conditions and congested/jam...