2 resultados para Statistical mean
em University of Queensland eSpace - Australia
Resumo:
Changes in arterial distensibility have been widely used to identify the presence of cardiovascular abnormalities like hypertension. Pulse wave velocity (PWV) has shown to be related to arterial distensibility. However, the lack of suitable techniques to measure PWV nonintrusively has impeded its clinical usefulness. Pulse transit time (PTT) is a noninvasive technique derived from the principle of PWV. PTT has shown its capabilities in cardiovascular and cardiorespiratory studies in adults. However, no known study has been conducted to understand the suitability and utility of PTT to estimate PWV in children. Two computational methods to derive PWV from PTT values obtained from 23 normotensive Caucasian children (19 males, aged 5-12 years old) from their finger and toe were conducted. Furthermore, the effects of adopting different postures on the PWV derivations were investigated. Statistical analyses were performed in comparison with two previous PWV studies conducted on children. Results revealed that PWV derived from the upper limb correlated significantly (P
Resumo:
Background Regression to the mean (RTM) is a statistical phenomenon that can make natural variation in repeated data look like real change. It happens when unusually large or small measurements tend to be followed by measurements that are closer to the mean. Methods We give some examples of the phenomenon, and discuss methods to overcome it at the design and analysis stages of a study. Results The effect of RTM in a sample becomes more noticeable with increasing measurement error and when follow-up measurements are only examined on a sub-sample selected using a baseline value. Conclusions RTM is a ubiquitous phenomenon in repeated data and should always be considered as a possible cause of an observed change. Its effect can be alleviated through better study design and use of suitable statistical methods.
