Su1429 Regression to the Mean and Treatment Effects in Gastroparesis

Abstract Research on teams in organizations tends to focus on understanding the causes of team performance with a focus on how to enjoy the benefits of team success and avoid the negative consequences of team failure. This paper instead asks the question, ‘what are some of the negative consequences of team success?’ A review of the literature on teams is augmented with research from cognitive science, sociology, occupational psychology, and psychology to explore the potential negative long-term consequences of teamwork success. The general topics of groupthink, overconfidence bias, regression to the mean, role overload, and strategy calcification are reviewed while discussing the implications for future research streams and practical team management.

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The analysis of the results of a rotation experiment on the use of straw and fertilizers

The Journal of Agricultural Science ◽

10.1017/s0021859600044609 ◽

1953 ◽

Vol 43 (1) ◽

pp. 77-88 ◽

Cited By ~ 10

Author(s):

H. D. Patterson

Keyword(s):

Present Experiment ◽

Treatment Effects ◽

Standard Errors ◽

Methods Of Analysis ◽

Seasonal Factors ◽

Long Term Experiments ◽

The Mean ◽

Linear Regressions

An experiment, designed to test different ways of using straw with fertilizers, and involving a three course rotation of crops, was carried out at Rothamsted between 1933 and 1951. The methods of analysis developed for this experiment are described in the present paper and demonstrated using yields of potatoes.Treatment effects of interest are given by the mean yields over all years and the linear regressions of yield on time. These estimates are straightforward but the evaluation of their errors is complicated by the existence of correlations due to the recurrence of treatments on the same plots. Further complications are introduced when, as frequently happens in long-term experiments, treatment effects show real variation from year to year. A method is given for estimating standard errors which include a contribution from this variation.The various relationships between yields and the uncontrolled seasonal factors can also be examined; in the present experiment there is some indication that the effects of treatments on yields of potatoes are influenced by the dates of planting.In other circumstances the analysis requires modifications, some of which are briefly considered.

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Are the Effects of Homeopathy Attributable to a Statistical Artefact? A Reanalysis of an Observational Study

Evidence-based Complementary and Alternative Medicine ◽

10.1155/2013/612890 ◽

2013 ◽

Vol 2013 ◽

pp. 1-7 ◽

Cited By ~ 3

Author(s):

Rainer Lüdtke ◽

Stefan N. Willich ◽

Thomas Ostermann

Keyword(s):

Quality Of Life ◽

Cohort Studies ◽

Summary Score ◽

Regression To The Mean ◽

Sf 36 ◽

The Mean ◽

Component Scores ◽

True Population ◽

Respective Standard Deviation

Background. Cohort studies have reported that patients improve considerably after individualised homeopathic treatment. However, these results may be biased by regression to the mean (RTM).Objective. To evaluate whether the observed changes in previous cohort studies are due to RTM and to estimate RTM adjusted effects.Methods. SF-36 quality-of-life (QoL) data from a German cohort of 2827 chronically diseased adults treated by a homeopath were reanalysed by Mee and Chua’s modifiedt-test.Results. RTM adjusted effects, standardized by the respective standard deviation at baseline, were 0.12 (95% CI: 0.06–0.19,P<0.001) in the mental and 0.25 (0.22–0.28,P<0.001) in the physical summary score. Small-to-moderate effects were confirmed for the most individual diagnoses in physical, but not in mental component scores. Under the assumption that the true population mean equals the mean of all actually diseased patients, RTM adjusted effects were confirmed for both scores in most diagnoses.Conclusions. Changes in QoL after treatment by a homeopath are small but cannot be explained by RTM alone. As all analyses made conservative assumptions, true RTM adjusted effects are probably larger than presented.

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Empirical methods for assessing meaningful neuropsychological change following epilepsy surgery

Journal of the International Neuropsychological Society ◽

10.1017/s1355617700001739 ◽

1996 ◽

Vol 2 (6) ◽

pp. 556-564 ◽

Cited By ~ 158

Author(s):

Stephen M. Sawrie ◽

Gordon J. Chelune ◽

Richard I. Naugle ◽

Hans O. Lüders

Keyword(s):

Epilepsy Surgery ◽

Intractable Epilepsy ◽

Practice Effects ◽

Cutoff Score ◽

Regression To The Mean ◽

Neuropsychological Battery ◽

Reliable Change ◽

Medical Interventions ◽

The Mean ◽

Test Retest Reliability

AbstractTraditional methods for assessing the neurocognitive effects of epilepsy surgery are confounded by practice effects, test-retest reliability issues, and regression to the mean. This study employs 2 methods for assessing individual change that allow direct comparison of changes across both individuals and test measures. Fifty-one medically intractable epilepsy patients completed a comprehensive neuropsychological battery twice, approximately 8 months apart, prior to any invasive monitoring or surgical intervention. First, a Reliable Change (RC) index score was computed for each test score to take into account the reliability of that measure, and a cutoff score was empirically derived to establish the limits of statistically reliable change. These indices were subsequently adjusted for expected practice effects. The second approach used a regression technique to establish “change norms” along a common metric that models both expected practice effects and regression to the mean. The RC index scores provide the clinician with a statistical means of determining whether a patient's retest performance is “significantly” changed from baseline. The regression norms for change allow the clinician to evaluate the magnitude of a given patient's change on 1 or more variables along a common metric that takes into account the reliability and stability of each test measure. Case data illustrate how these methods provide an empirically grounded means for evaluating neurocognitive outcomes following medical interventions such as epilepsy surgery. (JINS, 1996, 2, 556–564.)

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