Roxana A. Ion

Variation in Housing Design: Identifying Customer Preferences

House builders in different countries are exploring ways to deliver higher levels of customisation in housing design. To create such variety at acceptable cost, it is important to know how potential buyers of new houses prioritise the different elements such as bathroom, kitchen and roof type of a house design. For parts with a great variety, several alternative solutions could be created in advance while parts with a low variety can be produced as standard solutions for all homes, thereby taking advantage of economies of scale. This paper presents the findings of a vignette-based survey about the requirements for customisation among potential buyers of new houses in the Netherlands. Based on the survey, a list of priority housing attributes is derived. This priority listing is of great importance for building developers who offer (or are considering offering) customised housing. Although people generally prefer to have the opportunity to select from options, they will be less inclined to do so if this option also means a considerable increase in price. Therefore, this study also examines the trade-off relationship between the value customers place on variety and the maximum price that can be asked for a customised housing proposition. The paper concludes with implications of the studys findings for evaluating trade-off decisions between standardisation and customisation.

Field Reliability Prediction in Consumer Electronics Using Warranty Data

In innovative fast product development processes, such as consumer electronics, it is necessary to check as quickly as possible, using field data, whether the product reliability is at the right level. In consumer electronics, some major companies use the Warranty Call Rate (WCR) for this purpose. This paper discusses extensively the theoretical and practical drawbacks of the WCR. Subsequently, it is demonstrated, using a Weibull failure distribution, that only a few months after product launch, say three months, the warranty data offer the opportunity to estimate the parameters of the failure distribution. Of course, this requires that the warranty data are available in the quality department. Unfortunately, for some companies the field feedback information process from the repair centres to the quality department causes a delay of several months. These companies have to speed up their field feedback information process before they can fully take advantage of the proposed estimation procedure. Copyright

Non-parametric Shewhart control charts

Consider a training sample of independent random variables having an unknown strongly unimodal distribution. This sample is used to estimate the upper control limit (UCL) of a one-sided Shewhart control chart. The resulting control chart is meant to detect possible positive shifts of the distribution. A randomized estimator of the UCL is presented, the finite sample local optimality of the corresponding control chart is proved for sufficiently large sample sizes, and first-order asymptotic optimality of the error probabilities of this chart is derived.

Designing reliability information flows

It is well-known [Reliab. Eng. Syst. Saf. 75 (2002) 295] that in modern development processes it is essential to have an information flow structure that facilitates fast feedback from product users (customers) to departments at the front end, in particular development and production. As information is only relevant if it is used when taking decisions, this paper presents a guideline for building field feedback information flows that facilitate the decision taking during the product creation and realisation process. The guideline takes into consideration that the type of decisions depends on the span-of-control, therefore following Parsons [Structure and Process in Modern Societies (1990)] the span-of-control is subdivided into the following three levels: strategic, tactic, and executive. The guideline is illustrated with a case in which it is used for analysing the quality of existing field feedback flows.

Early reliability prediction in consumer electronics using Weibull distribution functions

This paper discusses the estimation of the failure probability during the warranty period. The failure probability is assumed to follow a Weibull distribution function. A case study based on example data based on the maximum likelihood estimation, is very useful in giving a fast feedback about product quality.

Bayesian model for early reliability prediction

This paper provides a Bayesian model for estimating the failure probability in the field, early after a product has been introduced to the market. First, the need for early reliability is recognized. Next, the Bayesian method is briefly explained after which it will be applied to early reliability prediction. Finally, it can be said that the model reduces the uncertainty of the prediction. The presented model has been applied in practice

Statistical model for estimating the failure probability in the field

This paper provides a statistical model for estimating the failure probability in the field given the known numbers of customers and reported failures. In this research we have studied two cases. In the first case we assume that the probabilities to fulfill the specification and to report the failure are known. In the second case we assume that these two probabilities are unknown, but we apply the Bayes method to incorporate engineering beliefs. We have proved in both cases that our new developed model yields good results. Further research is needed if more than one specification is tested.

Fast reliability prediction using Weibull distributions

Usually, in practice it is necessary to check as fast as possible, using field data, whether the product reliability is at the right level. This paper discusses the estimation of the failure probability during the warranty period given the limitations of field failure data.