The choice of a mixing distribution in duration models

The Hougaard mixing distribution is considered for a Weibull duration model. This distribution is flexible and also encompasses the gamma and the inverse Gaussian distributions making it useful in discriminating between alternate distributions

Specification Tests Based on the Heterogeneous Generalized Gamma Model of Duration: With an Application to Kennan\u27s Strike Data

In this paper, tests for neglected heterogeneity and functional form misspeciftcation of some commonly used parametric distributions are derived within a heterogeneous generalized gamma model. It is argued that the conventional test of heterogeneity may not be valid when the underlying hazard function is misspecified. Hence, if the estimated hazard function is deemed restrictive, tests for functional form misspecification should accompany any test of heterogeneity. An empirical illustration based on Kennan\u27s (1985) model of strikes is used to show that incorrect inferences may be drawn, as in a number of previous analyses, if the relevant restrictions are not tested jointly

Identifiability of the misspecified split hazard models

Unlike standard models, a split population hazard model allows the exit probability to be less than one. Although conceptually attractive, split models are prone to identification problems. In the reduced form estimation of the hazard function, the influence of split may not be distinguishable from that of neglected heterogeneity. For illustration, I use Monte Carlo simulations to highlight the problem of interpreting the structural parameters of the split Weibull and the Weibull-gamma models

Momentum Investing: The Case of High-Tech IPOs

We document significant momentum effects in the high-tech IPO aftermarket beyond the initial (underpricing) run-up. Cumulative market-adjusted returns (CMARs) reveal a striking pattern. A local peak of just over 10 percent is reached around 20 trading days post-IPO coinciding with the expiry of the “quiet period”. A global peak (of about 33 percent) is reached after 105 trading days. The CMAR decays fairly rapidly thereafter possibly in anticipation of the expiry of the six-month lockup period. Further, we find strong evidence of a linkage between technical ex-ante observable variables and the momentum build-up. We conjecture that visceral factors may at least partially underlie the investor behavior that gives rise to the bubble-like CMAR pattern

Vitamin B12 and/or Folate Deficiency is a Cause of Macro Thrombocytopenia

This retrospective study reveals that it is likely that vitamin B12 and / or folate deficiency is an important cause for isolated thrombocytopenia with larger than normal sized platelets. Data collection and interpretation from the laboratory has revealed this and as this can have further therapeutic utility, more studies on the subject are indicated. Hypothyroidism may also be another cause for the findings

Essentials of Business Statistics: communicating with numbers

Essentials of Business Statistics is designed for a new generation of students. This text sparks student interest and bridges the gap between how statistics is taught and how practitioners think about and apply statistical methods. Designed for a one-semester course, the emphasis is on communicating with numbers as opposed to just number crunching. Throughout the text, students are exposed to statistical information using real life examples. The focus is on writing and communicating results rather than merely the process of getting to the correct answer. This unique approach helps present the subject matter in a straightforward and relevant manner. As a result, students learn how to take data, apply it, and convey the results in a meaningful way

Foreign vs domestic ownership on debt reduction: an investigation of acquisition targets in Italy and Spain

This paper examines the role of foreign versus domestic ownership in reducing the debt levels of acquired firms in Italy and Spain over the period 2002–2010. Acknowledging that lower debt levels can mitigate the risk of failure and thus enhance the chances for a positive post-acquisition performance and survival, we particularly examine the causal effect of foreign and domestic acquisitions on two firm-level debt measures: gearing and short-term leverage. To estimate causal relationships, we control for selection bias by applying propensity score matching techniques. Our results indicate that foreign acquisition leads to a significant and steady reduction in the debt ratios of the target companies. In contrast, the relationship between domestic acquisition and debt reduction appears to be smaller and statistically less robust