194 research outputs found

    A quantum framework for likelihood ratios

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    The ability to calculate precise likelihood ratios is fundamental to many STEM areas, such as decision-making theory, biomedical science, and engineering. However, there is no assumption-free statistical methodology to achieve this. For instance, in the absence of data relating to covariate overlap, the widely used Bayes’ theorem either defaults to the marginal probability driven “naive Bayes’ classifier”, or requires the use of compensatory expectation-maximization techniques. Equally, the use of alternative statistical approaches, such as multivariate logistic regression, may be confounded by other axiomatic conditions, e.g., low levels of co-linearity. This article takes an information-theoretic approach in developing a new statistical formula for the calculation of likelihood ratios based on the principles of quantum entanglement. In doing so, it is argued that this quantum approach demonstrates: that the likelihood ratio is a real quality of statistical systems; that the naive Bayes’ classifier is a special case of a more general quantum mechanical expression; and that only a quantum mechanical approach can overcome the axiomatic limitations of classical statistics

    Analysing decision logs to understand decision-making in serious crime investigations

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    Objective: To study decision-making by detectives when investigating serious crime through the examination of Decision Logs to explore hypothesis generation and evidence selection. Background: Decision logs are used to record and justify decisions made during serious crime investigations. The complexity of investigative decision-making is well documented, as are the errors associated with miscarriages of justice and inquests. The use of decision logs has not been the subject of an empirical investigation, yet they offer an important window into the nature of investigative decision-making in dynamic, time-critical environments. Method: A sample of decision logs from British police forces was analyzed qualitatively and quantitatively to explore hypothesis generation and evidence selection by police detectives. Results: Analyses revealed diversity in documentation of decisions that did not correlate with case type, and identified significant limitations of the decision log approach to supporting investigative decision-making. Differences emerged between experienced and less experienced officers’ decision log records in exploration of alternative hypotheses, generation of hypotheses, and sources of evidential enquiry opened over phase of investigation. Conclusion: The practical use of decision logs is highly constrained by their format and context of use. Despite this, decision log records suggest that experienced detectives display strategic decision-making to avoid confirmation and satisficing that affect less experienced detectives. Application: Potential applications of this research include both training in case documentation and the development of new decision log media that encourage detectives, irrespective of experience, to generate multiple hypotheses and optimize the timely selection of evidence to test them

    Drawing the answers: Sketching to support free and probed recall by child witnesses and victims with autism spectrum disorder

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    The success of witness interviews in the criminal justice system depends on the accuracy of information obtained, which is a function of both amount and quality of information. Attempts to enhance witness retrieval such as mental reinstatement of context have been designed with typically developed adults in mind. In this paper, the relative benefits of mental and sketch reinstatement mnemonics are explored with both typically developing children and children with autism. Children watched a crime event video, and their retrieval of event information was examined in free and probed recall phases of a cognitive interview. As expected, typically developing children recalled more correct information of all types than children with autism during free and probed recall phases. Sketching during free recall was more beneficial for both groups in both phases in reducing the amount of incorrect items, but the relative effect of sketching on enhancing retrieval accuracy was greater for children with autism. The results indicate the benefits of choosing retrieval mnemonics that are sensitive to the specific impairments of autistic individuals, and suggest that retrieval accuracy during interviews can be enhanced, in some cases to the same level as that of typically developing individuals

    Comparison of the two most commonly used treatments for pyoderma gangrenosum: results of the STOP GAP randomised controlled trial

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    Objective To determine whether ciclosporin is superior to prednisolone for the treatment of pyoderma gangrenosum, a painful, ulcerating skin disease with a poor evidence base for management. Design Multicentre, parallel group, observer blind, randomised controlled trial. Setting 39 UK hospitals, recruiting from June 2009 to November 2012. Participants 121 patients (73 women, mean age 54 years) with clinician diagnosed pyoderma gangrenosum. Clinical diagnosis was revised in nine participants after randomisation, leaving 112 participants in the analysis set (59 ciclosporin; 53 rednisolone). Intervention Oral prednisolone 0.75 mg/kg/day compared with ciclosporin 4 mg/kg/day, to a maximum dose of 75 and 400 mg/day, respectively. Main outcome measures The primary outcome was speed of healing over six weeks, captured using digital images and assessed by blinded investigators. Secondary outcomes were time to healing, global treatment response, resolution of inflammation, self reported pain, quality of life, number of treatment failures, adverse reactions, and time to recurrence. Outcomes were assessed at baseline and six weeks and when the ulcer had healed (to a maximum of six months). Results Of the 112 participants, 108 had complete primary outcome data at baseline and six weeks (57 ciclosporin; 51 rednisolone). Groups were balanced at baseline. The mean (SD) speed of healing at six weeks was −0.21 (1.00) cm2/day in the ciclosporin group compared with −0.14 (0.42) cm2/day in the prednisolone group. The adjusted mean difference showed no between group difference (0.003 cm2/day, 95% confidence interval −0.20 to 0.21; P=0.97). By six months, ulcers had healed in 28/59 (47%) participants in the ciclosporin group compared with 25/53 (47%) in the prednisolone group. In those with healed ulcers, eight (30%) receiving ciclosporin and seven (28%) receiving prednisolone had a recurrence. Adverse reactions were similar for the two groups (68% ciclosporin and 66% prednisolone), but serious adverse reactions, especially infections, were more common in the prednisolone group. Conclusion Prednisolone and ciclosporin did not differ across a range of objective and patient reported outcomes. Treatment decisions for individual patients may be guided by the different side effect profiles of the two drugs and patient preference. Trial registration Current Controlled Trials ISRCTN35898459

    Is speed of healing a good predictor of eventual healing of pyoderma gangrenosum?

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    Background: Pyoderma gangrenosum is a rare inflammatory skin condition. The STOPGAP studies compared treatments for pyoderma gangrenosum using a primary outcome of healing speed at 6 weeks. Objective: Using data from both studies we assessed the predictive value of three early predictors for healing at 6 months - speed of healing, Investigator Global Assessment and resolution of inflammation, recorded at 2 and 6 weeks. Methods: Logistic regression models were applied and the effectiveness of the three measures was assessed through estimating the positive (PPV) and negative predictive values (NPV) and the area under the receiver operating characteristic curve (AUC). Results: The PPV and NPV at 6 weeks were 63.5% (95% CI:52.4%, 73.7%) and 74.6% (95% CI:62.5%, 84.5%) respectively for speed of healing; 80% (95% CI:68.7%, 88.6%) and 74.2% (95% CI:64.1%, 2.7%) for IGA; and 72.1% (95% CI:59.9%, 82.3%) and 68.1% (95% CI:57.7%, 77.3%) for resolution of inflammation. Investigator Global Assessment had the best combined PPV, NPV and AUC at 2 and 6 weeks. Limitations: We were limited by data available from the STOP GAP trial and cohort study. Conclusion: Speed of healing, Investigator Global Assessment and resolution of inflammation were all shown to be good predictors of eventual healing

    Smoking increases the risk of relapse after successful tuberculosis treatment

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    Background Recent tobacco smoking has been identified as a risk factor for developing tuberculosis, and two studies which have investigated its association with relapse of tuberculosis after completion of treatment had conflicting results (and did not control for confounding). The objective of this study was to investigate risk factors for tuberculosis relapse, with emphasis on smoking