In most clinical and experimental studies, the standard deviation (SD) and the estimated standard error of the mean (SEM) are used to present the characteristics of sample data and to explain statistical analysis results. However, some authors occasionally muddle the distinctive usage between the SD and SEM in medical literature. Because the process of calculating the SD and SEM includes differ...

As a nonstatistician, I have watched the discussion on this topic with interest (1–8). Dr. Curren-Everett and others make a clear statement that variability of results should always be reported using the standard deviation (SD) and not the standard error (SE). Others cited above variously agree and disagree with the guidelines published by Dr. Curren-Everett and others. The reasoning provided i...

OBJECTIVE This study examined the psychometric properties of the Young's Internet Addiction Test (IAT) in 844 Hong Kong Chinese adolescents (37.7% boys) with mean age of 15.9 (standard deviation = 3.5) years. METHODS Demographic items, Internet use habits, IAT, and the Revised Chen Internet Addiction Scale (CIAS-R) were administered. 3 percent of the participants were classified as addicted a...

PURPOSE To test the hypothesis that variability of conventional automated perimetry can be reduced using size V stimuli for patients with glaucomatous visual field damage. METHODS Ten patients with glaucoma and five age-matched control volunteers were tested with the Humphrey Field Analyzer program 24-2 or 30-2, after which the method of constant stimuli was used to measure frequency-of-seein...

BACKGROUND To quantify the variability among centers and to identify centers whose performance are potentially outside of normal variability in the primary outcome and to propose a guideline that they are outliers. METHODS Novel statistical methodology using a Bayesian hierarchical model is used. Bayesian methods for estimation and outlier detection are applied assuming an additive random cen...

The objective of the current study was to assess the separate and combined effects of marijuana and alcohol on actual driving performance. Eighteen subjects were treated with drugs and placebo according to a balanced, 6-way, crossover design. On separate evenings they were given weight calibrated Delta(9)-tetrahydrocannabinol (THC) doses of 0, 100 and 200 &mgr;g/kg with and without an alcohol d...