The Effect of Selective Data Omission on Type I Error Rates: A Simulation Study

There do not exist widely accepted guidelines or standards for identification and removal of outlying data in empirical research. There are sometimes significant incentives for researchers to discover particular research results. Researchers have been observed to use flexibility in outlier omission to selectively omit data in search of statistically significant findings. The degree to which this practice can affect the credibility of research findings is unknown. This study uses Monte Carlo simulation to estimate the propensity of certain types of selective outlier omission to inflate type I error rates in regression models. Simulations are designed to analyze posttest only control group design with no underlying intervention effect, such that any statistically significant findings represent type I errors. Omission of observations is simulated in an exploratory manner, such that observations are omitted and regressions are run iteratively until either a type I error is made or until a maximum trimming threshold is reached, whichever occurs first. Omission of observations based on z-score thresholds, a common research practice in some disciplines, is simulated. Additionally, omission from only of one tail of data—simulating the removal of only “disconfirming” observations—is analyzed. Simulations are performed using a variety of sample sizes and with samples drawn from several underlying population distributions. In all simulations, type I error rates are inflated; type I error rates are found to range from 7.86% to 100%, compared to the expected 5% in the absence of data omission

Maternal adverse childhood experiences and their association with preterm birth: secondary analysis of data from universal health visiting

BACKGROUND: Being born before full gestation can have short-term and life-long health implications, yet it remains difficult to determine the risk of preterm birth among expectant mothers. Across different health settings, increasing attention is given to the health and behavioural consequences of adverse childhood experiences (ACEs) such as child abuse or neglect, or exposure to harmful household environments (e.g. in which caregivers abuse alcohol), and the potential value of understanding these hidden harms when supporting individuals and families. A large international evidence base describes the association between childhood adversity and early years outcomes for mothers and children. However, the relationship between maternal ACEs and preterm birth has received far less attention. METHODS: Secondary analysis was carried out on anonymised cross-sectional data from health visiting services in south and west Wales that had previously captured information on mothers’ ACEs during routine contacts. Demographic data and information on mothers’ health were extracted from the Healthy Child Wales Programme. RESULTS: Half of all mothers sampled had experienced at least one ACE, with a history of ACEs more common among younger, white British mothers and those residing in deprived areas. Preterm birth was significantly independently associated with retrospective reports of childhood sexual abuse (adjusted odds ratio [AOR] = 3.83, 95% confidence interval [CI] = 1.19–12.32, p = 0.025), neglect (AOR = 7.60, 95%CI = 1.81–31.97, p = 0.006) and overall ACE exposure (AOR = 2.67, 95%CI = 1.14–6.23, p = 0.024), with one in ten mothers (10.0%) who experienced ≥4 ACEs having preterm birth. Sub-analyses revealed a more pronounced relationship among mothers with no known chronic health conditions, with those with ≥4 ACEs and no known chronic condition four times more likely to give birth preterm (AOR = 3.89, 95%CI = 1.40–10.80, p = 0.009). CONCLUSIONS: Findings highlight the importance of the entire maternal experience. The experience of childhood adversity can have a lasting impact into and beyond the prenatal period, potentially increasing the risk of preterm birth, even among otherwise healthy women. Increasing our understanding of the potential perinatal outcomes associated with ACEs can help to inform how maternity services and partners offer trauma-sensitive support to mitigate some of the risks of early parturition, as well as target intergenerational cycles of adversity and poor health. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12884-022-04454-z

On voxel-by-voxel accumulated dose for prostate radiation therapy using deformable image registration.

Since delivered dose is rarely the same with planned, we calculated the delivered total dose to ten prostate radiotherapy patients treated with rectal balloons using deformable dose accumulation (DDA) and compared it with the planned dose. The patients were treated with TomoTherapy using two rectal balloon designs: five patients had the Radiadyne balloon (balloon A), and five patients had the EZ-EM balloon (balloon B). Prostate and rectal wall contours were outlined on each pre-treatment MVCT for all patients. Delivered fractional doses were calculated using the MVCT taken immediately prior to delivery. Dose grids were accumulated to the last MVCT using DDA tools in Pinnacle3 TM (v9.100, Philips Radiation Oncology Systems, Fitchburg, USA). Delivered total doses were compared with planned doses using prostate and rectal wall DVHs. The rectal NTCP was calculated based on total delivered and planned doses for all patients using the Lyman model. For 8/10 patients, the rectal wall NTCP calculated using the delivered total dose was less than planned, with seven patients showing a decrease of more than 5% in NTCP. For 2/10 patients studied, the rectal wall NTCP calculated using total delivered dose was 2% higher than planned. This study indicates that for patients receiving hypofractionated radiotherapy for prostate cancer with a rectal balloon, total delivered doses to prostate is similar with planned while delivered dose to rectal walls may be significantly different from planned doses. 8/10 patients show significant correlation between rectal balloon anterior-posterior positions and some VD values

The Effect of Selective Data Omission on Type I Error Rates: A Simulation Study

There do not exist widely accepted guidelines or standards for identification and removal of outlying data in empirical research. There are sometimes significant incentives for researchers to discover particular research results. Researchers have been observed to use flexibility in outlier omission to selectively omit data in search of statistically significant findings. The degree to which this practice can affect the credibility of research findings is unknown. This study uses Monte Carlo simulation to estimate the propensity of certain types of selective outlier omission to inflate type I error rates in regression models. Simulations are designed to analyze posttest only control group design with no underlying intervention effect, such that any statistically significant findings represent type I errors. Omission of observations is simulated in an exploratory manner, such that observations are omitted and regressions are run iteratively until either a type I error is made or until a maximum trimming threshold is reached, whichever occurs first. Omission of observations based on z-score thresholds, a common research practice in some disciplines, is simulated. Additionally, omission from only of one tail of data—simulating the removal of only “disconfirming” observations—is analyzed. Simulations are performed using a variety of sample sizes and with samples drawn from several underlying population distributions. In all simulations, type I error rates are inflated; type I error rates are found to range from 7.86% to 100%, compared to the expected 5% in the absence of data omission

Exploring the health and service utilisation of general practice patients with a history of adverse childhood experiences (ACEs):an observational study using electronic health records

Objectives To examine the relationships between adverse childhood experiences (ACEs), chronic health and health service utilisation among a sample of general practice patients.Design Cross-sectional observational study using anonymised data from electronic health records for 763 patients.Setting Four general practices in northwest England and North Wales.Outcome measures Patient demographic data (age, gender); body mass index; self-reported smoking status; self-reported ACEs; diagnosis of chronic health conditions; current mental health problems; total number of service contacts and repeat medication use in the previous 6 months.Results A history of ACEs (experiencing abuse or neglect as a child, and/or growing up in a household characterised by violence, substance use, mental health problems or criminal behaviour) was strongly independently associated with current mental health problems, smoking and chronic obstructive pulmonary disease, showing a dose–response relationship with level of ACE exposure. Medication use and contact were significantly greater among patients with high ACE exposure (≥4 ACEs), compared with those with no ACEs. However, contrary to findings from population studies, health service utilisation was not significantly different for patients with increased ACE exposure (1–3 ACEs) and their ACE-free counterparts.Conclusions Findings highlight the contribution ACEs make to unequal distributions of risk to health and well-being and patterns of health service use in the UK

Variability and Proper Motion of X-ray Knots in the Jet of Centaurus A

Accepted to ApJ, 14 pages, 8 figures, 2 tablesWe report results from Chandra observations analyzed for evidence of variability and proper motion in the X-ray jet of Centaurus A. Using data spanning 15 yr, collective proper motion of 11.3 ± 3.3 mas yr -1 , or 0.68 ± 0.20c, is detected for the fainter X-ray knots and other substructure present within the jet. The three brightest knots (AX1A, AX1C, and BX2) are found to be stationary to an upper limit of . Brightness variations up to 27% are detected for several X-ray knots in the jet. For the fading knots, BX2 and AX1C, the changes in spectral slope expected to accompany synchrotron cooling are not found, ruling it out and placing upper limits of ≃80 μG for each of their magnetic field strengths. Adiabatic expansion can account for the observed decreases in brightness. Constraints on models for the origin of the knots are established. Jet plasma overrunning an obstacle is favored as the generator of stationary knots, while moving knots are likely produced either by internal differences in jet speed or the late stages of jet interaction with nebular or cloud material.Peer reviewe