A new procedure for testing equivalence in comparative bioavailability and other clinical trials

The problem of testing for equivalence in clinical trials is restated here in terms of the proper clinical hypotheses and a simple classical frequentist significance test based on the central t distribution is derived. This method is then shown to be more powerful than the methods based on usual (shortest) and symmetric confidence intervals.

We begin by considering a noncentral t statistic and then consider three approximations to it. A simulation is used to compare actual test sizes to the nominal values in crossover and completely randomized designs. A central t approximation was the best. The power calculation is then shown to be based on a central t distribution, and a method is developed for obtaining the sample size required to obtain a specified power. For the approximations, a simulation compares actual powers to those obtained for the t distribution and confirms that the theoretical results are close to the actual powers.     

Detecting changes in task length due to task‐switching in the presence of repeated length‐biased sampling

Clinical work is characterised by frequent interjection of external prompts causing clinicians to switch from a primary task to deal with an incoming secondary task, a phenomenon associated with negative effects in experimental studies. This is an important yet underexplored aspect of work in safety critical settings in general, since an increase in task length due to task‐switching implies reduced efficiency, while decreased length suggests hastening to compensate for the increased workload brought by the unexpected secondary tasks, which is a potential safety issue. In such observational settings, longer tasks are naturally more likely to have one or more task‐switching events: a form of length bias. To assess the effect of task‐switching on task completion time, it is necessary to estimate counterfactual task lengths had they not experienced any task‐switching, while also accounting for length bias. This is a problem that appears simple at first, but has several counterintuitive considerations resulting in a uniquely constrained solution space. We review the only existing method based on an assumption that task‐switches occur according to a homogeneous Poisson process. We propose significant extensions to flexibly incorporate heterogeneity that is more representative of task‐switching in real‐world contexts. The techniques are applied to observations of emergency physicians’ workflow in two hospital settings.     

Multi-horizon Markowitz portfolio performance appraisals: A general approach

This article extends the analysis of multi-horizon mean-variance portfolio analysis in the Morey and Morey [Mutual fund performance appraisals: a multi-horizon perspective with endogenous benchmarking. Omega 1999;27:241–58] article in several ways. First, instead of either proportionally contracting risk dimensions or proportionally expanding return dimensions, a more general efficiency measure simultaneously attempts to reduce risk and to expand return over all time periods. Second, a duality relation is established between this generalized multi-horizon efficiency measure and an indirect mean-variance utility function, underscoring the natural interpretation of this generalized efficiency measure in terms of investor's preferences. Furthermore, the need to properly apply time discounting in multi-horizon mean-variance portfolio problems is argued for. An empirical illustration based on the original mutual fund data set in Morey and Morey [Mutual fund performance appraisals: a multi-horizon perspective with endogenous benchmarking. Omega 1999;27:241–58] is added to contrast the new and the original approaches.     

Bovine Spongiform Encephalopathy Maternal Cohort Study—Exploratory Analysis

The bovine spongiform encephalopathy (BSE) maternal cohort study supports a role both for direct maternal transmission and for inherited genetic susceptibilty to the BSE agent. Additional data from the main BSE database do not resolve whether the risk of direct maternal transmission of BSE from dam to calf is concentrated in the interval within 5 months before the onset of BSE in the dam, as data from the BSE maternal cohort study suggest. The reason for this is that we cannot rely, as our analysis requires, on the survival of calves or traceability of the dam being independent of the interval from the birth of a calf to onset of BSE in the dam. Accordingly, for the present, we place most weight on evidence from the BSE maternal cohort study. Direct maternal transmission of the BSE agent from dam to calf has not been ruled out; vertical transmission of the new variant Creutzfeldt–Jakob disease (NVCJD) from mother with NVCJD to baby is therefore also possible. Actions to quantify, and minimize, the transmission risk, if any, from a mother with NVCJD to her baby, or to delivery teams, should be taken without delay.     

Automatic processes and the appraisal of sexual stimuli: Toward an information processing model of sexual arousal

A model of sexual arousal is presented that highlights the interaction between automatic and controlled cognitive processes and proposes that different levels of cognitive processing can differentially affect subjective and physiological sexual arousal. In addition, two studies are presented in which the role of automatic processes was explored using a priming paradigm. Subjects were sexually functional men. In the first study an effect of priming was found on penile erection. Unexpectedly, responses were lower in sexual than in neutral trials. In the second study support was found, using a behavioral measure (decision time), for the notion that the meaning of sexual stimuli can be perceived in a fast, automatic manner. Priming was most successful at lower levels of stimulus accessibility. The model and experimental approach presented in this article render starting points for new research on response discordance, gender differences in the processing of sexual stimuli, and inhibition of sexual response.     

Estimation of proportions by group testing with retesting of positive groups

Abstract

When estimating a proportion p by group testing, and it is desired to increase precision, it is sometimes impractical to obtain additional individuals but it is possible to retest groups formed from the individuals within the groups that test positive at the first stage. Hepworth and Watson assessed four methods of retesting, and recommended a random regrouping of individuals from the first stage. They developed an estimator of p for their proposed method, and, because of the analytic complexity, used simulation to examine its variance properties. We now provide an analytical solution to the variance of the estimator, and compare its performance with the earlier simulated results. We show that our solution gives an acceptable approximation in a reasonable range of circumstances.     

Multidisciplinary Child Protection Decision Making About Physical Abuse: Determining Substantiation Thresholds and Biases

The current study examined the threshold at which multidisciplinary child protection team (CPT) professionals substantiate physical abuse allegations and the extent that they utilize potentially biased constructs in their decision making when presented with the same case evidence. State legal definitions of child maltreatment are broad. Therefore, the burden of interpretation is largely on CPT professionals who must determine at what threshold physical acts by parents surpass corporal discipline and constitute child physical abuse. Biased or subjective decisions may be made if certain case-specific characteristics or CPT professionals' personal characteristics are used in making physical abuse determinations. Case vignettes with visual depictions of inflicted injuries were sent to CPT professionals in Florida and their substantiation decisions, personal beliefs about corporal discipline, and coercive discipline were collected. Results of the study demonstrated relatively high agreement among professionals across vignettes about what constitutes physical abuse. Further, CPT professionals strongly considered their perceptions of the severity of inflicted injuries in substantiation decisions. Although case specific characteristics did not bias decisions in a systematic way, some CPT professional characteristics influenced the substantiation of physical abuse. Practice implications and future directions of research are discussed.     

Rationality,external norms,and the epistemic value of menus

Ever since Sen’s criticism of internal consistency properties of choice, there exists a perception that the standard rational choice approach has difficulties in coping with the existence of external norms, or the information a menu of choice might convey to a decision maker. This article provides a brief survey of possible responses to these criticisms of traditional rational choice theory. We review approaches to the internalization of external norms as well as ways to formulate norm-conditional rationalizability. Furthermore, we illustrate how the epistemic value of an opportunity set can be incorporated into rational choice theory.