This paper examines the power of the sporadic v. familial method as applied to schizophrenia and major depression. The model used assumes aetiological heterogeneity with a subpopulation of cases due to a ‘major’ environmental event and the remainder resulting from a generalized single major locus. The findings suggest that, for sample sizes to which it is commonly applied, the sporadic v. familial classification has low power to detect aetiological heterogeneity. When applied to nuclear families, substantial power requires at a minimum 100–150 proband families. If the proportion of environmental cases in the population is low, or the ‘test’ for environmental aetiology in probands does not have high sensitivity and specificity, the required sample sizes are considerably larger. Adding monozygotic twins increases the power of the method, but including second-degree relatives does not. The optimal approach to the sporadic v. familial method will differ as a function of the frequency of the disorder and the relative effort and expense of examining probands versus family members. Other methods should be considered for discriminating genetic and environmental forms of illness.

The value of a new method of scoring the General Health Questionnaire (CGHQ) has been assessed in a representative sample of 6317 British community residents aged 18 +. The CGHQ, which takes account of the chronicity of psychiatric symptoms, is found to be superior to the conventional scoring method in yielding a wider range of scores, a more normal distribution and in its close association to a well validated measure of neurotic illness.

On the other hand, the conventional GHQ and the CGHQ score appear equally sensitive to a number of socio-demographic variables, including social class, marital status and employment. An important finding is that the two methods identify different individuals as cases. Compared with the GHQ, the CGHQ identifies a higher proportion of the middle-aged. The implications of these findings with respect to the optimal method of scoring the GHQ are discussed.

Visual Analogue Scales (VAS) provide a simple technique for measuring subjective experience. They have been established as valid and reliable in a range of clinical and research applications, although there is also evidence of increased error and decreased sensitivity when used some subject groups. Decisions concerned with the choice of scoring interval, experimental design, and statistical analysis for VAS have in some instances been based on convention, assumption and convenience, highlighting the need for more comprehensive assessment of individual scales if this versatile and sensitive measurement technique is to be used to full advantage.

Alternative procedures for coding nonresponse on the Mini-Mental State Examination (as error or as correct) results in different classification of 13% of a random sample of 1931 subjects aged 60 and over. Comparison of responders' and nonresponders' ability to perform activities of daily living, and examination of the relative difficulty level of omitted items indicates that, in epidemiological surveys, scoring nonresponse as error is more likely to be correct.