Targeting childhood obesity in schools: an examination of the stability and utility of the Value Added Index

12 pagesBackground: High rates of childhood obesity and overweight have promoted interest in school-based interventions. As a way to identify schools with high unexpected prevalence of obesity and the greatest need, Procter and associates developed a ‘Value Added Index’ (VAI). It compares rates of obesity in entry level and advanced students in elementary schools, quantifying the extent to which rates for advanced students are higher than what would be expected given entry level rates and socio-demographic characteristics. Methods: This paper replicates their analysis using data over a 4 year time span from 17 schools in the western United States. Our analysis compared results obtained with the relatively complicated mixed-model approach, which was used by Procter and associates, and a more simple linear regression, which could be easily used by local school officials. Results were also compared across the 4 years for which data were available. Results: Identical results were found when the two methods were compared. There was little stability in the rank ordering of schools, based on the VAI, from 1 year to another. Conclusions: Our results cast doubts on the utility of the VAI for policy makers and suggest policy makers consider a universalistic, rather than targeted, approach to interventions

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements