A procedure for estimating the reliability of sets of ratings in terms of the intraclass correlation coefficient is discussed. The procedure is based upon the analysis of variance and the estimation of variance components. For the one-way classification the intraclass correlation coefficient defined as the ratio of variances can be interpreted as a correlation coefficient. Caution, however, is urged in the application of the definition to a two-way model, i.e., one in which between-rater variance is removed. It is maintained that the frequent use of the standard definition of the one-way intraclass correlation coefficient applied to the two-way classification is not a proper procedure if in fact the coefficient is to be interpreted as a correlation coefficient. Definitions for reliability obtained from the two-way models are given which can legitimately be considered correlation coefficients.

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HILE THE EXACT BIOLOGIcal cascade associated with Alzheimer disease (AD) is only partially understood, many potential biomarkers of this disease process are known. 1 Two of the most obvious candidates are ␤-amyloid 1-42 and tau proteins, as they are intimately related to the pathognomonic features of amyloid plaques and neurofibrillary tangles in the AD brain. 2,3 Multiple previous studies have reported decreases in cerebrospinal fluid (CSF) measures of ␤-amyloid. 4-7 Similarly, CSF measures of tau have routinely showed considerable elevations of this peptide in AD cases worldwide. 7-12 Some authors have reported that these 2 measures alone can accurately differentiate clinically diagnosed AD cases from controls more than 85% of the time. 7,13 Studies of CSF in AD patients have used widely varying methods and nomenclature for assessing and describ-Author Affiliations are listed at the end of this article.

Many persons with schizophrenia may be challenged by the cognitive demands of an informed consent process for research participation. In many cases, their reduced capacity can be compensated by a more intensive educational intervention as part of the informed consent process.

This paper briefly reviews the most frequently used and misused intraclass correlation-analysis of variance (ANOVA) reliability measures. Recommendations are made for the one-way ANOVA intraclass correlation and against the use of several coefficients: Winer's so-called "anchor point method," Kuder-Richardson Formula Number 20, and the Spearman-Brown prediction formula. The computation of the intraclass correlation coefficient via two-way ANOVA is not encouraged. Several uses and misuses of reliability coefficients applied to dichotomous data are also illustrated.