Multiple choice questions: to guess or not to guess

Multiple choice question papers in which the student has a 'don't know' option are widely used in undergraduate and postgraduate examinations in Medicine. In the present study students' performance in papers with a 'don't know' option has been compared with their performance when they are instructed to answer all the questions. By completing questions left unanswered (i.e. 'don't know' options) students were able to increase their score significantly and the rank order of the students in class is changed. Answers omitted may indicate complete ignorance or various degrees of knowledge. It is concluded that the 'don't know' option in multiple choice question papers favours the bold and test-wise student and in consequence their validity as a measure of achievement may suffer. Papers in which the student is instructed to answer all the questions are to be preferred to those in common use where there is a 'don't know' option.     

The effect of stimulus probability on P3 in the respiratory-related evoked potential

The present study investigated the effect of target stimulus probability on the P3 component of the respiratory-related evoked potential (RREP). A single respiratory stimulus paradigm was employed where normal breaths served as standard stimuli and occluded breaths presented at various probability levels served as target stimuli. EEG was recorded from 29 channels in young adults in two conditions. In Condition 1, occlusions were presented at target probabilities of 0.5, 0.33, 0.25, 0.2, 0.1, and 0.05, that is, every 2nd, 3rd, 4th, 5th, 10th, and 20th breath. Order of target probability presentation varied randomly. Condition 2 used the same target probabilities, but held breathing rate constant by using a paced respiration task. Results indicated that P3 amplitude was significantly affected by stimulus probability, such that the component showed an inverse relationship with probability. This effect was similar between conditions. However, P3 amplitude reduced and latency increased when the secondary task of paced respiration was introduced. These data suggest that models developed to describe the effect of stimulus probability on the amplitude of visual and auditory P3 components are applicable to the respiratory somatosensory modality.     

Fluoro-deoxy-glucose positron emission tomography for evaluation of indeterminate lung nodules: assigning a probability of malignancy may be preferable to binary readings

OBJECTIVE: To assess the diagnostic value of fluorine-18 fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) using standard uptake values (SUV) in the differential diagnoses of indeterminate pulmonary nodules. Specifically, we assessed the probability of malignancy for various SUV ranges, and compared the diagnostic efficacy of SUV with and without correction for partial volume effects on the basis of lesion size. METHODS: The FDG-PET scans performed on 158 patients with biopsy-proven pulmonary lesions seen on computed tomography (CT) scan were retrospectively reviewed. Histopathological confirmation was obtained to establish the diagnosis of the lesions. A region of interest (ROI) was drawn for each lesion, and FDG uptake was quantified (SUV(raw)). The SUV(raw) values were normalized for the "size" of the pulmonary lesions measured on CT (SUV(size)). Sensitivity and specificity of FDG-PET for pulmonary lesions <2 cm in diameter or > or =2 cm in diameter were determined at SUV cutoff values of 2.5. The areas under the receiver-operating characteristic (ROC) curve for SUV(raw) and SUV(size) regarding the presence of malignancy were compared for statistical differences. The frequency of malignant lesions for each range of SUVs was obtained to produce the probability of cancer (POC). RESULTS: The mean SUV(raw) was 3.17 +/- 2.76 and 9.18 +/- 6.72 for benign and malignant lesions, respectively. When a SUV(raw) value of 2.5 was used as a cutoff, sensitivity and specificity were 89% and 51%, respectively, for all lesion sizes. The sensitivity and specificity at a cutoff SUV(raw) of 2.5 for lesions less than 2 cm in diameter were 75% and 72%, respectively, and 92% and 41% for lesions 2 cm or greater, respectively. The sensitivity and specificity at a cutoff SUV(size) of 2.5 were 88% and 42%, respectively. The area under the ROC curves for SUV(raw) and SUV(size) was 0.816 and 0.743, respectively (P value 0.034). When the SUV(raw) was divided into three groups, the probability of malignancy was 26% when the SUV(raw) was <2, 57% for 2 < or = SUV(raw) < 6, and 89% for SUV(raw) > or = 6. CONCLUSIONS: The FDG-PET is a reasonably accurate and useful tool for characterizing the nature of indeterminate pulmonary lesions, although the specificity was not as high as that reported in the literature, probably owing in part to our patient population and selection bias. Our data suggest that reporting the results of PET studies as a probability rather than as positive or negative for malignancy would be more useful for further management decision making. Correction of SUVs for tumor size did not improve accuracy.     

Men’s dietary patterns in relation to infertility treatment outcomes among couples undergoing in vitro fertilization

Purpose(s)To evaluate the relationship of men’s dietary patterns with outcomes of in vitro fertilization (IVF).MethodsThis is a prospective cohort study including 231 couples with 407 IVF cycles, presented at an academic fertility center from April 2007 to April 2018. We assessed diet with a validated food frequency questionnaire and identified Dietary Pattern 1 and Dietary Pattern 2 using principal component analysis. We evaluated adjusted probability of IVF outcomes across the quartiles of the adherence to two dietary patterns by generalized linear mixed models.ResultsMen had a median age of 36.8 years and BMI of 26.9 kg/m². Women’s median age and BMI were 35.0 years and 23.1 kg/m², respectively. Adherence to Dietary Pattern 1 (r_Pearson=0.44) and Dietary Pattern 2 (r_Pearson=0.54) was positively correlated within couples. Adherence to Dietary Pattern 1 was positively associated with sperm concentration. A 1-unit increase in this pattern was associated with a 13.33 (0.71–25.96) million/mL higher sperm concentration. However, neither Dietary Pattern 1 nor Dietary Pattern 2 was associated with fertilization, implantation, clinical pregnancy, or live birth probabilities.ConclusionsData-derived dietary patterns were associated with semen quality but unrelated to the probability of successful IVF outcomes.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10815-021-02251-9.     

Probability estimation models for prediction of BRCA1 and BRCA2 mutation carriers: COS compares favourably with other models

Background Accurate risk assessment is essential to genetic counselling for a family history of cancer. Several empiric and computer-based risk assessment models have been developed to estimate a counselee's probability of being a carrier of mutation in BRCA1 and/or 2 genes, and to predict the risk of developing breast cancer. The COS model was developed from the better-known BRCAPro model to estimate risk of carriage of BRCA1 or 2 mutation. The COS model remains to be validated in a population discrete from that used for its development. Methods Four probability estimation models including COS, Manchester scoring system (MSS), BOADICEA and Tyrer-Cuzick (T-C) were applied to 275 Scottish families tested for BRCA1/2 mutations ascertained through regional genetics centres to ascertain models' sensitivity, specificity and accuracy. A subset of 130 families from Grampian (North and Northeast Scotland) was used to assess the models' ability to estimate the prevalence of BRCA1/2 mutation carriers. Sensitivity, specificity and ROC plots were used to ascertain models' individual performance, in terms of number of cancer cases, type of cancer and age of diagnosis of breast cancer. Results The COS and MSS models demonstrated the greatest sensitivities and area under ROC curves for the majority of family structures. They also showed the highest sensitivities (91-92%) and AUCs (76-78%) for the entire dataset overall. However, BOADICEA and T-C had the highest specificities for the majority of the family structures. BOADICEA and T-C generated the best estimates for the prevalence of mutations in the population; BOADICEA was more accurate for BRCA1 and T-C for BRCA2. Conclusion The COS and MSS models are the most effective models for use in clinical practice to select families for mutation analysis, but BOADICEA and T-C are more accurate for estimating mutation prevalence within a population.     

概率对冲突信息诱发的事件相关电位N270的影响

目的:研究刺激概率对颜色冲突信息诱发的事件相关电位N270的影响。方法:将四种颜色随机组合的刺激对分为三组:一组,在该组刺激中颜色相同的刺激对与不同的刺激对各占50％的概率;二组颜色不同的占85％,相同的占15％的概率;三组颜色不同的概率占15％,相同的占85％。受试者的任务:辨别前后呈现的两个刺激(第一个刺激S1,第二个刺激S2)颜色是否相同。结果:在颜色冲突(两个刺激颜色不同)事件中,S2刺激可诱发出一显著的事件相关电位负波(N270),该负波并不出现在非冲突事件中,且N270的振幅不受概率的影响。结论:N270是反映脑内特定冲突信息探知系统的神经电活动指标,与N2b不同,不受刺激概率的影响。     

Probably Good Diagrams for Learning: Representational Epistemic Recodification of Probability Theory

The representational epistemic approach to the design of visual displays and notation systems advocates encoding the fundamental conceptual structure of a knowledge domain directly in the structure of a representational system. It is claimed that representations so designed will benefit from greater semantic transparency, which enhances comprehension and ease of learning, and plastic generativity, which makes the meaningful manipulation of the representation easier and less error prone. Epistemic principles for encoding fundamental conceptual structures directly in representational schemes are described. The diagrammatic recodification of probability theory is undertaken to demonstrate how the fundamental conceptual structure of a knowledge domain can be analyzed, how the identified conceptual structure may be encoded in a representational system, and the cognitive benefits that follow. An experiment shows the new probability space diagrams are superior to the conventional approach for learning this conceptually challenging topic.     

Community venue exposure risk estimator for the COVID-19 pandemic

Complexities of virus genotypes and the stochastic contacts in human society create a big challenge for estimating the potential risks of exposure to a widely spreading virus such as COVID-19. To increase public awareness of exposure risks in daily activities, we propose a birthday-paradox-based probability model to implement in a web-based system, named COSRE (community social risk estimator) and make in-time community exposure risk estimation during the ongoing COVID-19 pandemic. We define exposure risk to mean the probability of people meeting potential cases in public places such as grocery stores, gyms, libraries, restaurants, coffee shops, offices, etc. Our model has three inputs: the real-time number of active and asymptomatic cases, the population in local communities, and the customer counts in the room. With COSRE, possible impacts of the pandemic can be explored through spatiotemporal analysis, e.g., a variable number of people may be projected into public places through time to assess changes of risk as the pandemic unfolds. The system has potential to advance understanding of the true exposure risks in various communities. It introduces an objective element to plan, prepare and respond during a pandemic. Spatial analysis tools are used to draw county-level exposure risks of the United States from April 1 to July 15, 2020. The correlation experiment with the new cases in the next two weeks shows that the risk estimation model offers promise in assisting people to be more precise about their personal safety and control of daily routine and social interaction. It can inform business and municipal COVID-19 policy to accelerate recovery.