Marginal analysis of longitudinal count data in long sequences: Methods and applications to a driving study

Most of the available methods for longitudinal data analysis are designed and validated for the situation where the number of subjects is large and the number of observations per subject is relatively small. Motivated by the Naturalistic Teenage Driving Study (NTDS), which represents the exact opposite situation, we examine standard and propose new methodology for marginal analysis of longitudinal count data in a small number of very long sequences. We consider standard methods based on generalized estimating equations, under working independence or an appropriate correlation structure, and find them unsatisfactory for dealing with time-dependent covariates when the counts are low. For this situation, we explore a within-cluster resampling (WCR) approach that involves repeated analyses of random subsamples with a final analysis that synthesizes results across subsamples. This leads to a novel WCR method which operates on separated blocks within subjects and which performs better than all of the previously considered methods. The methods are applied to the NTDS data and evaluated in simulation experiments mimicking the NTDS.Comment: Published in at http://dx.doi.org/10.1214/11-AOAS507 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Face the Nation - Senator Edmund S. Muskie Interviewed for CBS News

Senator Edmund S. Muskie interview for CBS News\u27 Face the Nation. Topics include the 1972 campaign, the Nixon Administration, the U.S. economy, Vietnam

Experimental Effects of Pre-Drive Arousal on Teenage Simulated Driving Performance in the Presence of a Teenage Passenger

Teenage passengers increase teenage driving risk, but this may be conditional on events and emotions immediately preceding driving. An experimental simulation study evaluated the effect of pre-drive arousal on risky driving in the presence of a confederate teenage passenger. In a two-by-two between-subjects design, participants were randomized to high or low pre-drive arousal and passenger present or not present conditions. Prior to the drive participants played the Nintendo Wii video game, Rock BandTM. In the high-arousal condition participants stood while playing high-energy Beatles songs; in the low arousal condition participants sat while playing low-energy Beatles songs. The manipulation produced differences in arousal by group. Group differences in risky driving were in the expected direction, but were not statistically significant at p = .05 on any of the three outcome measures, which included Failed to Stop (failing to stop at signalized intersections in the dilemma zone), Percent Time in Red (in intersections), and Pass Slow Vehicle (electing to pass a slow vehicle)

Cognitive demands of face monitoring: Evidence for visuospatial overload

Young children perform difficult communication tasks better face to face than when they cannot see one another (e.g., Doherty-Sneddon & Kent, 1996). However, in recent studies, it was found that children aged 6 and 10 years, describing abstract shapes, showed evidence of face-to-face interference rather than facilitation. For some communication tasks, access to visual signals (such as facial expression and eye gaze) may hinder rather than help children’s communication. In new research we have pursued this interference effect. Five studies are described with adults and 10- and 6-year-old participants. It was found that looking at a face interfered with children’s abilities to listen to descriptions of abstract shapes. Children also performed visuospatial memory tasks worse when they looked at someone’s face prior to responding than when they looked at a visuospatial pattern or at the floor. It was concluded that performance on certain tasks was hindered by monitoring another person’s face. It is suggested that processing of visual communication signals shares certain processing resources with the processing of other visuospatial information

Storm surge and ponding explain mangrove dieback in southwest Florida following Hurricane Irma

Mangroves buffer inland ecosystems from hurricane winds and storm surge. However, their ability to withstand harsh cyclone conditions depends on plant resilience traits and geomorphology. Using airborne lidar and satellite imagery collected before and after Hurricane Irma, we estimated that 62% of mangroves in southwest Florida suffered canopy damage, with largest impacts in tall forests (>10?m). Mangroves on well-drained sites (83%) resprouted new leaves within one year after the storm. By contrast, in poorly-drained inland sites, we detected one of the largest mangrove diebacks on record (10,760?ha), triggered by Irma. We found evidence that the combination of low elevation (median?=?9.4?cm?asl), storm surge water levels (>1.4?m above the ground surface), and hydrologic isolation drove coastal forest vulnerability and were independent of tree height or wind exposure. Our results indicated that storm surge and ponding caused dieback, not wind. Tidal restoration and hydrologic management in these vulnerable, low-lying coastal areas can reduce mangrove mortality and improve resilience to future cyclones.ECU Open Access Publishing Support Fun

A Functional Data Analysis Approach for Circadian Patterns of Activity of Teenage Girls

Background: Longitudinal or time-dependent activity data are useful to characterize the circadian activity patterns and to identify physical activity differences among multiple samples. Statistical methods designed to analyze multiple activity sample data are desired, and related software is needed to perform data analysis. Methods: This paper introduces a functional data analysis (fda) approach to perform a functional analysis of variance (fANOVA) for longitudinal circadian activity count data and to investigate the association of covariates such as weight or body mass index (BMI) on physical activity. For multiple age group adolescent school girls, the fANOVA approach is developed to study and to characterize activity patterns. The fANOVA is applied to analyze the physical activity data of three grade adolescent girls (i.e., grades 10, 11, and 12) from the NEXT Generation Health Study 2009–2013. To test if there are activity differences among girls of the three grades, a functional version of the univariate F-statistic is used to analyze the data. To investigate if there is a longitudinal (or time-dependent activity count) difference between two samples, functional t-tests are utilized to test: (1) activity differences between grade pairs; (2) activity differences between low-BMI girls and high-BMI girls of the NEXT study. Results: Statistically significant differences existed among the physical activity patterns for adolescent school girls in different grades. Girls in grade 10 tended to be less active than girls in grades 11 & 12 between 5:30 and 9:30. Significant differences in physical activity were detected between low-BMI and high-BMI groups from 8:00 to 11:30 for grade 10 girls, and low-BMI group girls in grade 10 tended to be more active. Conclusions: The fda approach is useful in characterizing time-dependent patterns of actigraphy data. For two-sample data defined by weight or BMI values, fda can identify differences between the two time-dependent samples of activity data. Similarly, fda can identify differences among multiple physical activity time-dependent datasets. These analyses can be performed readily using the fda R program

Higher self-reported physical activity Is associated with lower systolic blood pressure: The Dietary Intervention Study in Childhood (DISC)

Objective: Children participating in a dietary clinical trial were studied to assess physical activity patterns in boys and girls longitudinally from late childhood through puberty; and to determine the association of level of physical activity on systolic blood pressure (SBP), low density lipoprotein (LDL) cholesterol, and body mass index (BMI). Patients and Methods: In the Dietary Intervention Study in Childhood (DISC), a randomized clinical trial of a reduced saturated fat and cholesterol diet in 8-10 year olds with elevated LDL, a questionnaire that determined time spent in five intensity levels of physical activity was completed at baseline and at 1 and 3 years. A MET score was calculated for weekly activity; hours per week were calculated for intense activities. We hypothesized that weekly self-reported physical activity would be associated with lower SBP, LDL, and BMI over three years. Longitudinal data analyses were performed for each outcome (SBP, LDL, and BMI) using generalized estimating equations with MET score per week as the independent variable adjusted for visit, gender, and Tanner stage (BMI was included in models for SBP and LDL). Results: The initial study cohort comprised 663 youths (362 male; age 9.7 years, 301 female; age 9.0 years) of whom 623 (94%) completed the 3-year visit. For every 100 MET-hours of physical activity, there was a decrease of 1.15 mmHg of SBP (p=0.0038). There was a 1.28 mg/dl decline in LDL (p=0.10) for a similar energy expenditure. For BMI, an analysis of intense physical activity showed that for every 10 hours of intense activity, there was a trend toward significance with a 0.2 kg/m2 decrease (p=0.06). Conclusion: Children with elevated cholesterol who lead a more physically active lifestyle have lower SBP and a trend toward lower LDL over a 3-year interval. Long-term participation in intense physical activity may reduce BMI as well

Planet Occurrence within 0.25 AU of Solar-type Stars from Kepler

We report the distribution of planets as a function of planet radius (R_p), orbital period (P), and stellar effective temperature (Teff) for P < 50 day orbits around GK stars. These results are based on the 1,235 planets (formally "planet candidates") from the Kepler mission that include a nearly complete set of detected planets as small as 2 Earth radii (Re). For each of the 156,000 target stars we assess the detectability of planets as a function of R_p and P. We also correct for the geometric probability of transit, R*/a. We consider first stars within the "solar subset" having Teff = 4100-6100 K, logg = 4.0-4.9, and Kepler magnitude Kp < 15 mag. We include only those stars having noise low enough to permit detection of planets down to 2 Re. We count planets in small domains of R_p and P and divide by the included target stars to calculate planet occurrence in each domain. Occurrence of planets varies by more than three orders of magnitude and increases substantially down to the smallest radius (2 Re) and out to the longest orbital period (50 days, ~0.25 AU) in our study. For P < 50 days, the radius distribution is given by a power law, df/dlogR= k R^\alpha. This rapid increase in planet occurrence with decreasing planet size agrees with core-accretion, but disagrees with population synthesis models. We fit occurrence as a function of P to a power law model with an exponential cutoff below a critical period P_0. For smaller planets, P_0 has larger values, suggesting that the "parking distance" for migrating planets moves outward with decreasing planet size. We also measured planet occurrence over Teff = 3600-7100 K, spanning M0 to F2 dwarfs. The occurrence of 2-4 Re planets in the Kepler field increases with decreasing Teff, making these small planets seven times more abundant around cool stars than the hottest stars in our sample. [abridged]Comment: Submitted to ApJ, 22 pages, 10 figure

Does Speaking Two Dialects in Daily Life Affect Executive Functions? An Event-Related Potential Study

Whether using two languages enhances executive functions is a matter of debate. Here, we take a novel perspective to examine the bilingual advantage hypothesis by comparing bidialect with mono-dialect speakers’ performance on a non-linguistic task that requires executive control. Two groups of native Chinese speakers, one speaking only the standard Chinese Mandarin and the other also speaking the Southern-Min dialect, which differs from the standard Chinese Mandarin primarily in phonology, performed a classic Flanker task. Behavioural results showed no difference between the two groups, but event-related potentials recorded simultaneously revealed a number of differences, including an earlier P2 effect in the bi-dialect as compared to the mono-dialect group, suggesting that the two groups engage different underlying neural processes. Despite differences in the early ERP component, no between-group differences in the magnitude of the Flanker effects, which is an index of conflict resolution, were observed in the N2 component. Therefore, these findings suggest that speaking two dialects of one language does not enhance executive functions. Implications of the current findings for the bilingual advantage hypothesis are discussed