Weak Calibration of a Visible Light Positioning System Based on a Position-Sensitive Detector: Positioning Error Assessment

Reduced deployment and calibration requirements are key for scalable and cost-effective indoor positioning systems. In this work, we propose a low-complexity, weak calibration procedure for an indoor positioning system based on infrastructure lighting and a positioning-sensitive detector. The proposed calibration relies on genetic algorithms to obtain the relevant system parameters in the real positioning environment without a priori information, and requires a low number of simple measurements. The achievable performance of the proposal was assessed by direct comparison with a formal offline calibration method requiring complex dedicated infrastructure and instruments. The comparative error assessment showed that the maximum accuracy reduction compared to the significantly more costly formal calibration was below 25 mm, and the overall absolute positioning error was smaller than 35 mm with orientation errors of around 0.25°. The performance achieved with the proposed weak calibration procedure is sufficient for many indoor positioning applications and largely reduces the cost and complexity of setting up the positioning system in real environments.

Validity of comorbidity adjustment scores in estimating in-hospital mortality in individual subgroups of race/ethnicity

Aim: To examine the validity of race/ethnicity-specific comorbidity adjustment scores in estimating in-hospital mortality. Materials & methods: Using 2007–2014 data from the State Inpatient Databases (SID), we compared the performance of derived race/ethnicity-specific composite scores to the existing scores and binary Elixhauser comorbidity measures at estimating in-hospital mortality. Results: In the overall validation sample (N = 9,564,277), our index (c = 0.80; 95% CI: 0.79–0.80) discriminated better than the van Walraven score (c = 0.79; 95% CI: 0.79–0.79), SID 29 (c = 0.78; 95% CI: 0.78–0.79) and SID 30 (c = 0.78; 95% CI: 0.78–0.78), but was not superior to the binary indicators (c = 0.80; 95% CI: 0.80–0.80). Similar findings were observed in individual populations of White and Black patients. All models showed weak calibration. Conclusion: Race/ethnicity-specific indexes discriminated slightly better than existing composite measures at modeling in-hospital mortality in individual subgroups of race/ethnicity.

What the Annual National Assessments can tell us about learning deficits over the education system and the school career

<p>Much hope is placed on education systems to reduce socioeconomic learning gaps. But in South Africa, uneven functioning of the school system widens learning gaps.<br />This paper analyses education performance using ANA data. Weak calibration and inter-temporal or inter-grade comparability of ANA test scores limit their usefulness for measuring learning gains. However, relative performance provides meaningful information on learning gaps and deficits. A reference group that is roughly on track to achieve the TIMSS average is used to estimate the performance required in each grade to perform at TIMSS’ low international benchmark. <br />By Grade 4, patterns across quintiles of on track performance approximate matric exemption patterns. Viewed differently, academic and labour market prospects may be bleak for children who are no longer on track. Improvement in outcomes requires greater emphasis on the Foundation Phase or earlier, before learning deficits have grown to extreme levels observed by the middle of primary school. This statement is true whether deficits arise from weak early instruction, or simply because a disadvantaged home environment requires early remedial action. The emphasis on the early grades that this analysis of the ANAS suggests to is contrary to the conclusions drawn from the ANA results by policy makers, that weak test scores in Mathematics in Grade 9 require major interventions in that grade.</p>

What the Annual National Assessments can tell us about learning deficits over the education system and the school career

Much hope is placed on education systems to reduce socioeconomic learning gaps. But in South Africa, uneven functioning of the school system widens learning gaps.This paper analyses education performance using ANA data. Weak calibration and inter-temporal or inter-grade comparability of ANA test scores limit their usefulness for measuring learning gains. However, relative performance provides meaningful information on learning gaps and deficits. A reference group that is roughly on track to achieve the TIMSS average is used to estimate the performance required in each grade to perform at TIMSS’ low international benchmark. By Grade 4, patterns across quintiles of on track performance approximate matric exemption patterns. Viewed differently, academic and labour market prospects may be bleak for children who are no longer on track. Improvement in outcomes requires greater emphasis on the Foundation Phase or earlier, before learning deficits have grown to extreme levels observed by the middle of primary school. This statement is true whether deficits arise from weak early instruction, or simply because a disadvantaged home environment requires early remedial action. The emphasis on the early grades that this analysis of the ANAS suggests to is contrary to the conclusions drawn from the ANA results by policy makers, that weak test scores in Mathematics in Grade 9 require major interventions in that grade.