Fisher information in weighted distributions

Suppose that a density f_θ (x) belongs to an exponential family, but that inference about θ must be based on data that are obtained from a density that is proportional to W(x)f_θ(x). The authors study the Fisher information about θ in observations obtained from such weighted distributions and give conditions under which this information is greater than under the original density. These conditions involve the hazard- and reversed-hazard-rate functions.     

Evaluation of a synthetic method of estimation for small areas

A synthetic estimator is one of the simplest estimators for a small area, and it has several variants. In this paper, a ratio-synthetic estimator is proposed and compared with the existing synthetic estimator (Ghangurde & Singh, 1977) and it is observed that the gain due to stratification in the case of a synthetic estimator reduces proportional to the domain coverage.     

On totally balanced block designs for competition effects

Competition between neighbouring units in field experiments is a serious source of bias. The study of a competing situation needs construction of an environment in which it can happen and the competing units have to appear in a predetermined pattern. This paper describes methods of constructing incomplete block designs balanced for neighbouring competition effects. The designs obtained are totally balanced in the sense that all the effects, direct and neighbours, are estimated with the same variance. The efficiency of these designs has been computed as compared to a complete block design balanced for neighbours and a catalogue has also been prepared.     

Filtering via approximate Bayesian computation

Approximate Bayesian computation (ABC) has become a popular technique to facilitate Bayesian inference from complex models. In this article we present an ABC approximation designed to perform biased filtering for a Hidden Markov Model when the likelihood function is intractable. We use a sequential Monte Carlo (SMC) algorithm to both fit and sample from our ABC approximation of the target probability density. This approach is shown to, empirically, be more accurate w.r.t.?the original filter than competing methods. The theoretical bias of our method is investigated; it is shown that the bias goes to zero at the expense of increased computational effort. Our approach is illustrated on a constrained sequential lasso for portfolio allocation to 15 constituents of the FTSE 100 share index.     

A note on the estimation methods of crop production at the block level

This paper presents a method of estimation of crop-production statistics at smaller geographical levels like a community development block (generally referred to as a block) to make area-specific plans for agricultural development programmes in India. Using available district-level data on crop yield from crop-cutting experiments and data on auxiliary variables from various administrative sources, a suitable regression model is fitted. The fitted model is then used to predict the crop production at the block level. Some scaled estimators are also developed using predicted estimates. An empirical study is also carried out to judge the merits of the proposed estimators.     

Estimation of population product in presence of non-response in successive sampling

The design of this paper is to examine the problem of estimation of finite population product in mail surveys for the current occasion in the context of sampling on two occasions is attempted when there is non-response on both the occasions. Estimators for the current occasion are derived as a particular case when there is non-response on first and second occasion only. The gain in efficiency of the proposed estimate over the direct estimate using no information gathered on the first occasion is computed. The proposed strategy has been compared with other estimators. An empirical study is carried out to study the performance of the proposed strategy.     

A note on an IPPS sampling scheme

Summary This paper presents a new IPPS sampling scheme possessing some desirable properties and providing an unbiased and non-negative variance estimator under H-T model. An empirical study is also undertaken to examine the performance of the scheme compared to some standard sampling schemes. The authors are grateful to the referees for providing many helpful suggestions on the earlier draft of the paper.     

Underwriting and Calls of Convertible Bonds*

We model convertible bond calls under asymmetric information where, unlike Harris and Raviv (1985), we consider a nonzero call price and a call notice period. In the model, the use of underwriters conveys negative information. Consequently, the stock price decline is greater for underwritten calls than for nonunderwritten calls. Furthermore, underwritten calls are made earlier and when the conversion option is less deep in the money. Underwriting commissions and the stock price decline associated with a call are negatively related to the extent that the conversion option is in the money before the call. Empirical evidence in this paper and Singh, Cowan, and Nayar (1991) are consistent with the model's predictions.