On the History of the Correction for Grouping, 1873–1922

The correction for grouping is a sum of two terms, the first depending on the length of the grouping interval, the second being a periodic function of the position. Thiele (1873) studied the second term, but missed the first. Sheppard (1898) studied the first term, but missed the second. Bruns (1906) derived the first term as the aperiodic term of a Fourier series and the second as the sum of the periodic terms. He found the correction to the coefficients of the Gram–Charlier series and proved that the second term is negligible for a grouped normal distribution with at least eight groups. Independently, Fisher (1922) used the same method to derive the correction to the moments. For the normal distribution with a grouping interval less than the standard deviation Fisher proved that the second term is negligible compared with the first and with the standard error of the first four moments. Moreover, he proved that the estimates of the mean and the standard deviation obtained by the method of moments for a grouped sample with Sheppard's corrections have nearly the same variances as the maximum likelihood estimates, thus providing a new and compelling reason for using Sheppard's corrections.     

The effect of MRP lot sizing on actual cumulative lead times in multi-level systems

This study investigates how different lot sizing techniques influence the cumulative lead time for multi-level production-inventory systems controlled by material requirements planning (MRP). Theoretical approaches, a numerical example, as well as simulation are used to analyse and illustrate the combined effect of lot sizing at different product structure levels. It is shown that lot-sizing requirements for more than a single period, such as fixed period requirements, period under quantity, Silver Meal algorithm, as well as economic order quantity will lead to longer actual cumulative lead times than would be expected, when taking the item lead times along the critical path through the product structure into account. Consequently, MRP will underestimate the cumulative lead time and will require a longer planning horizon. We show that the extension of the cumulative lead techniques covering the time is a lot-sizing related phenomenon and cannot be accounted for by, e.g. using safety lead time. Lot-sizing techniques with multi-period coverage will only occasionally provide the 'expected' cumulative lead time. We also show that average and maximum throughput times, as well as throughput time variability increases with increasing time-period coverage of lots.     

Space-time Multi Type Log Gaussian Cox Processes with a View to Modelling Weeds

Log Gaussian Cox processes as introduced in Moller et al. (1998) are extended to space-time models called log Gaussian Cox birth processes. These processes allow modelling of spatial and temporal heterogeneity in time series of increasing point processes consisting of different types of points. The models are shown to be easy to analyse yet flexible enough for a detailed statistical analysis of a particular agricultural experiment concerning the development of two weed species on an organic barley field. Particularly, the aspects of estimation, model validation and intensity surface prediction are discussed.     

Effects of psychosocial interventions on behavioural problems in youth: A close look at Cochrane and Campbell reviews

Research indicates that a number of psychosocial interventions are effective for reducing behavioural problems in youth. These interventions are now often included on best practice lists aiming to facilitate informed treatment choices among practitioners. However, analyses in neighbouring research areas have highlighted serious shortcomings in how primary studies are analysed and how studies are synthesised in research reviews. This study took a closer look at the evidence of efficacy for psychosocial interventions that aim to reduce behavioural problems in youth, as shown in systematic research reviews by the Cochrane and the Campbell Collaborations (n = 8). The findings suggest a bias towards overemphasising the efficacy of the interventions in several reviews, an over‐confidence in the validity of the findings in some reviews and, overall, a somewhat uncertain evidence base for the efficacy of the interventions. Systematic reviews are crucial for summarising research but more attention to methodological issues may be needed in this area.     

Towards a Multi‐level Approach on Frontline Interactions in the Public Sector: Institutional Transformations and the Dynamics of Real‐time Interactions

This study develops a multi‐level approach on frontline interactions in the public sector. Previous research suggests that detailed analyses of frontline interactions are essential to our understanding of how welfare services take shape when policies and rules are applied and negotiated in individual cases. The dynamics and performances of real‐time interactions have, however, rarely been analyzed as such. This study shows how the methods developed in the field of Conversation Analysis can contribute to this research. Our multi‐level approach integrates analyses of the policy‐ and institutional transformations that shape conditions for frontline interactions; and analyses of how policies and rules are evoked, negotiated and reshaped in the turn‐by‐turn organization and performances of interaction. The approach is applied on an analysis of how rules regarding financial aid are applied in an authority highly affected by changes in welfare policy towards standardization and detailed regulations. The empirical case is the Swedish Board for Study Support. The empirical study includes analyses of documents, interviews and analyses of taped telephone conversations. The study shows how institutional arrangements of standardization, detailed regulations, monitoring and depersonalization, structure the frontline work and shape narrow frames for officials' discretion in interactions with clients. The study also shows how rules are invoked and negotiated in recurrent practices in the interaction: in the careful design of decisions; in the investigations of alternatives and exceptions from the rules in order to find solutions to the client's problems. The analyses of concrete interactional practices clearly indicate that also a rule‐governed work dominated by task discretion involves recurrent negotiations, flexibility and local policy‐making.     

A Multifactorial Risk Prioritization Framework for Foodborne Pathogens

We develop a prioritization framework for foodborne risks that considers public health impact as well as three other factors (market impact, consumer risk acceptance and perception, and social sensitivity). Canadian case studies are presented for six pathogen‐food combinations: Campylobacter spp. in chicken; Salmonella spp. in chicken and spinach; Escherichia coli O157 in spinach and beef; and Listeria monocytogenes in ready‐to‐eat meats. Public health impact is measured by disability‐adjusted life years and the cost of illness. Market impact is quantified by the economic importance of the domestic market. Likert‐type scales are used to capture consumer perception and acceptance of risk and social sensitivity to impacts on vulnerable consumer groups and industries. Risk ranking is facilitated through the development of a knowledge database presented in the format of info cards and the use of multicriteria decision analysis (MCDA) to aggregate the four factors. Three scenarios representing different stakeholders illustrate the use of MCDA to arrive at rankings of pathogen‐food combinations that reflect different criteria weights. The framework provides a flexible instrument to support policymakers in complex risk prioritization decision making when different stakeholder groups are involved and when multiple pathogen‐food combinations are compared.     

Bayes Estimates for the Price and Income Elasticities of Alcoholic Beverages in Finland From 1955 to 1980

The Lindley–Smith theory of Bayes estimates for multiple regression equations with exchangeability between the regression coefficients of the individual equations is extended to the case in which a first-order autoregressive process generates the regression coefficients. The ensuing formulas are applied to study monthly Finnish consumption of alcohol. The point of this application is that exchangeability between the regression coefficients is less than we can assess beforehand when there is a natural ordering, in this case according to chronological time, of the equations. Still, the general task of the Lindley–Smith estimators, to consider the combined data when estimating individual regression coefficients, is a relevant one.     

Windows to the Soul? Deliberate Eye Contact as a Cue to Deceit

Although people overwhelmingly believe that liars avoid eye contact, meta-analyses of deception literature have shown a non-significant relationship between gaze and deception. In the present experiment we measured eye movements in an innovative way. We coded the extent to which interviewees deliberately made eye contact with the interviewer. Liars take their credibility less for granted than truth tellers. They therefore may have a greater desire to be convincing and hence more inclined to monitor the interviewer to determine whether they seem to be being believed. We therefore hypothesized that liars would give more appearance of deliberately making eye contact than truth tellers (a relationship which opposes the stereotypical belief that liars look away). A total of 338 passengers at an international airport told the truth or lied about their forthcoming trip. As well as the deliberate eye contact variable, we coded the amount of time the interviewees looked away from the interviewer (e.g., gaze aversion), which is typically examined in deception research. Liars displayed more deliberate eye contact than truth tellers, whereas the amount of gaze aversion did not differ between truth tellers and liars.