The Estimation of Causal Effects from Observational Data

When experimental designs are infeasible, researchers must resort to the use of observational data from surveys, censuses, and administrative records. Because assignment to the independent variables of observational data is usually nonrandom, the challenge of estimating causal effects with observational data can be formidable. In this chapter, we review the large literature produced primarily by statisticians and econometricians in the past two decades on the estimation of causal effects from observational data. We first review the now widely accepted counterfactual framework for the modeling of causal effects. After examining estimators, both old and new, that can be used to estimate causal effects from cross-sectional data, we present estimators that exploit the additional information furnished by longitudinal data. Because of the size and technical nature of the literature, we cannot offer a fully detailed and comprehensive presentation. Instead, we present only the main features of methods that are accessible and potentially of use to quantitatively oriented sociologists.Sociolog

RETROCAM: A Versatile Optical Imager for Synoptic Studies

We present RETROCAM, an auxiliary CCD camera that can be rapidly inserted into the optical beam of the MDM 2.4m telescope. The speed and ease of reconfiguring the telescope to use the imager and a straightforward user interface permit the camera to be used during the course of other observing programs. This in turn encourages RETROCAM's use for a variety of monitoring projects.Comment: 6 pages, 6 figures, Accepted by A

The Spatial Structure of An Accretion Disk

Based on the microlensing variability of the two-image gravitational lens HE1104-1805 observed between 0.4 and 8 microns, we have measured the size and wavelength-dependent structure of the quasar accretion disk. Modeled as a power law in temperature, T proportional to R^-beta, we measure a B-band (0.13 microns in the rest frame) half-light radius of R_{1/2,B} = 6.7 (+6.2 -3.2) x 10^15 cm (68% CL) and a logarithmic slope of beta=0.61 (+0.21 -0.17) for our standard model with a logarithmic prior on the disk size. Both the scale and the slope are consistent with simple thin disk models where beta=3/4 and R_{1/2,B} = 5.9 x 10^15 cm for a Shakura-Sunyaev disk radiating at the Eddington limit with 10% efficiency. The observed fluxes favor a slightly shallower slope, beta=0.55 (+0.03 -0.02), and a significantly smaller size for beta=3/4.Comment: 5 pages, 4 figures, submitted to Ap

Simultaneous Estimation of Time Delays and Quasar Structure

We expand our Bayesian Monte Carlo method for analyzing the light curves of gravitationally lensed quasars to simultaneously estimate time delays and quasar structure including their mutual uncertainties. We apply the method to HE1104-1805 and QJ0158-4325, two doubly-imaged quasars with microlensing and intrinsic variability on comparable time scales. For HE1104-1805 the resulting time delay of (Delta t_AB) = t_A - t_B = 162.2 -5.9/+6.3 days and accretion disk size estimate of log(r_s/cm) = 15.7 -0.5/+0.4 at 0.2 micron in the rest frame are consistent with earlier estimates but suggest that existing methods for estimating time delays in the presence of microlensing underestimate the uncertainties. We are unable to measure a time delay for QJ0158-4325, but the accretion disk size is log(r_s/cm) = 14.9 +/- 0.3 at 0.3 micron in the rest frame.Comment: 21 pages, 6 figures, submitted to Ap

Contemporary reproductive outcomes for patients with polycystic ovary syndrome: a retrospective observational study

Context Polycystic ovary syndrome (PCOS) is the commonest cause of anovulatory infertility and may be associated with adverse pregnancy and neonatal outcomes. However, it is difficult to establish how much of this risk is due to PCOS and how much to obesity. Objective To determine the impact of PCOS upon fertility, pregnancy and neonatal outcomes. Design and setting Data were extracted from the Clinical Practice Research Datalink (CPRD), a longitudinal anonymized primary care research database in the UK. Patients with a diagnosis of PCOS were matched to controls (1:2) by age (+/-1 year), BMI (+/- 3 units) and CPRD practice. Standardised fertility ratios (SFR) before and after diagnosis (index date) were calculated. Rates of miscarriage, pre-eclampsia, gestational diabetes, premature delivery, delivery method and neonatal outcomes were compared. Results 9,068 women with PCOS matched study criteria. Prior to index date the SFR for patients with PCOS was 0.80 (95% CI 0.77-0.83); following index date it was 1.16 (1.12-1.20). The adjusted odds ratios (OR) for miscarriage (1.70; 1.56-1.84), pre-eclampsia (1.32; 1.16-1.49), gestational diabetes (1.41; 1.2-1.66) and premature delivery (1.25; 1.1-1.43) were all increased compared to controls. Of PCOS births, 27.7% were by Caesarean section compared with 23.7% of controls (1.13; 1.05-1.21). Infants born to mothers with PCOS had an increased risk of neonatal jaundice (1.20; 1.03-1.39) and respiratory complications (1.20; 1.06-1.37). Conclusions PCOS is associated with subfertility but fertility rates are restored to those of the background population following diagnosis. Pregnancy complications and adverse neonatal outcomes are more prevalent for women with PCOS independently of obesity

Long Term Benefits for Women in a Science, Technology, Engineering, and Mathematics Living-Learning Community

Science, technology, engineering and math (STEM) degrees provide opportunities for economic mobility. Yet women, underrepresented minority (URM), and first-generation college students remain disproportionately underrepresented in STEM fields. This study examined the effectiveness of a living-learning community (LLC) for URM and first-generation first-year women interested in STEM. The authors utilized a matched sample post-hoc analysis to examine undergraduate and graduate degree attainment in science related fields for women who participated in the Women in Science Residence Program (WISERP) LLC compared to matched controls. The control group was matched on twelve characteristics that are associated with retention in STEM. First-generation college students in the LLC were significantly more likely to receive an undergraduate degree in science; URM students were more likely to receive an undergraduate degree in a science related field, nearly three times as likely to receive a master’s degree in science and more than three times as likely to receive a graduate degree in science compared to their matched controls. The results indicate that a one-year intervention can meaningfully impact persistence of at-risk populations in attaining STEM bachelor’s degrees and in enrolling in STEM graduate programs and invite further investigation into the factors contributing to the beneficial impact of LLCs

A Consistent Picture Emerges: A Compact X-ray Continuum Emission Region in the Gravitationally Lensed Quasar SDSS J0924+0219

We analyze the optical, UV, and X-ray microlensing variability of the lensed quasar SDSS J0924+0219 using six epochs of Chandra data in two energy bands (spanning 0.4-8.0 keV, or 1-20 keV in the quasar rest frame), 10 epochs of F275W (rest-frame 1089A) Hubble Space Telescope data, and high-cadence R-band (rest-frame 2770A) monitoring spanning eleven years. Our joint analysis provides robust constraints on the extent of the X-ray continuum emission region and the projected area of the accretion disk. The best-fit half-light radius of the soft X-ray continuum emission region is between 5x10^13 and 10^15 cm, and we find an upper limit of 10^15 cm for the hard X-rays. The best-fit soft-band size is about 13 times smaller than the optical size, and roughly 7 GM_BH/c^2 for a 2.8x10^8 M_sol black hole, similar to the results for other systems. We find that the UV emitting region falls in between the optical and X-ray emitting regions at 10^14 cm < r_1/2,UV < 3x10^15 cm. Finally, the optical size is significantly larger, by 1.5*sigma, than the theoretical thin-disk estimate based on the observed, magnification-corrected I-band flux, suggesting a shallower temperature profile than expected for a standard disk.Comment: Replaced with accepted version to Ap

A Long View of Polluting Industry and Environmental Justice in Baltimore

Purpose This study examines the density of polluting industry by neighborhoods in Baltimore over the long term, from 1950 to 2010, to determine if high pollution burdens correspond spatially with expected demographic and housing variables predicted in the environmental justice literature. For 1960–1980 we use data on heavy industry from Dun and Bradstreet directories and for 1990–2010 the US EPA’s Toxics Release Inventory to calculate a Hazards Density Index. Drawing on the decennial censuses for 1960–2010, we populate census tracts from corresponding years with data on race, ethnicity, educational attainment, income, and housing tenure. Findings Density of polluting industry is positively correlated with low-income neighborhoods and renter-occupied housing in 1960 and by 2010 with white, Hispanic, and low educational attainment populations. In general, over time density of polluting facilities shifts from an association with wealth to race and ethnicity while educational attainment remains a significant variable throughout. This study confirms earlier analyses on Baltimore that white neighborhoods are more likely than African–American neighborhoods (1990–2010) to contain polluting facilities but reveals for the first time that educational attainment is also significant. The paper concludes with a discussion of the Baltimore Sustainability Plan and its weak efforts to address persistent environmental injustices