Biomedical subjects

Jeffrey D Blume

Publications and source records attributed to Jeffrey D Blume.

3 recordsLinked to original sources

PubMed2002

Likelihood methods for measuring statistical evidence.

Focused on interpreting data as statistical evidence, the evidential paradigm uses likelihood ratios to measure the strength of statistical evidence. Under this paradigm, re-examination of accumulating evidence is encouraged because (i) the likelihood ratio, unlike a p-value, is unaffected by the number of examinations and (ii) the probability of observing strong misleading evidence is naturally low, even for study designs that re-examine the data with each new observation. Further, the controllable probabilities of observing misleading and weak evidence provide assurance that the study design is reliable without affecting the strength of statistical evidence in the data. This paper illustrates the ideas and methods associated with using likelihood ratios to measure statistical evidence. It contains a comprehensive introduction to the evidential paradigm, including an overview of how to quantify the probability of observing misleading evidence for various study designs. The University Group Diabetes Program (UGDP), a classic and still controversial multi-centred clinical trial, is used as an illustrative example. Some of the original UGDP results, and subsequent re-analyses, are presented for comparison purposes.

Biometry↗

PubMed2002

Young maternal age associated with increased risk of postneonatal death.

OBJECTIVE: To determine whether full-term, healthy infants born to early adolescent mothers (15 years old and younger) are at higher risk of postneonatal death compared with infants of adult mothers. METHODS: We combined the comprehensive 1996 and 1997 United States birth cohorts to compare postneonatal mortality rates among maternal age groups. With postneonatal death as our main outcome measure, we used multivariable logistic regression to model adjusted odds ratios. RESULTS: The postneonatal mortality rate for infants born to mothers 15 years old and younger was substantially higher (3.2 per 1000) than that of infants born to mothers 23-29 years old (0.8 per 1000) and remained substantially higher after adjusting for maternal race or ethnicity. Even after adjusting for maternal race or ethnicity, prenatal care utilization, and marital status, infants born to early adolescent mothers had a three-fold higher risk (odds ratio 3.0, 95% confidence interval 2.5, 3.6) of postneonatal death compared with adult mothers. CONCLUSION: Healthy infants born to early adolescent mothers are at increased risk of postneonatal death. Many of these deaths are potentially preventable; therefore, developing targeted postnatal support services specifically designed to address the needs of healthy infants born to adolescent mothers might have a positive effect on the lives of these children.

Adolescent↗

PubMed2002

Batting performance of wood and metal baseball bats.

INTRODUCTION/PURPOSE: Although metal baseball bats are widely believed to outperform wood bats, there are few scientific studies which support this. In a batting cage study, Greenwald et al. found that baseballs hit with a metal bat traveled faster than those hit with a wood bat, but the factors responsible for this difference in bat performance remain unidentified. The purpose of this study was to determine the effects of swing speed, impact location, and elastic properties of the bat on batted ball speeds. METHODS: The pitched ball, batted ball, and swings of two wood and five metal baseball bats by 19 different players were tracked in three dimensions at 500 Hz using a passive infrared motion analysis system. RESULTS: Increases in the batted ball speeds of metal bats over those of wood bats resulted from faster swing speeds and higher elastic performance with an apparent increase in the ball-bat coefficient of restitution. The contribution of these variables to batted ball speed differed with metal bat model. The "sweet spot" associated with maximum batted ball speeds was located approximately the same distance from the tip of wood bats as it was from metal bats. CONCLUSIONS: The variables that correlated with differences between metal and wood bat performance, and most notably differences in the percentage of faster batted balls, were identified using a novel kinematic analysis of the ball and bat. These variables and their correlation with bat performance should be applicable to other players and bats, although more skilled players and higher performing bats would likely result in even faster batted ball speeds.

Acceleration↗