Lincoln E. Moses

Estimating Diagnostic Accuracy from Multiple Conflicting Reports A New Meta-analytic Method

Reports of diagnostic accuracy often differ. The authors present a method to summarize disparate reports that uses a logistic transformation and linear regression to produce a summary receiver operating characteristic curve. The curve is useful for summarizing a body of diagnostic accuracy literature, comparing technologies, detecting outliers, and finding the optimum operating point of the test. Examples from clinical chemistry and diagnostic radiology are provided. By extending the logic of meta-analysis to diagnostic testing, the method provides a new tool for technology assessment. Key words: meta-analysis; sensitivity and specificity; decision support; data interpretation, statistical; regression analysis; diagnostic accuracy. (Med Decis Making 1993;13:313-321)

AIDS: Sexual Behavior and Intravenous Drug Use

Since the acquired immunodeficiency syndrome (AIDS) epidemic is partly a social phenomenon changes in the social behaviors that spread the disease are as necessary as the development of vaccines and other therapies. To help in the design implementation and evaluation of programs to curb the spread of AIDS there is a need for greater understanding of the human behaviors that transmit human immunodeficiency virus (HIV) infection as well as the social contexts in which these behaviors occur. Toward this end the US Committee on AIDS Research and the Behavioral Social and Statistical Sciences was asked to: 1) describe what is known about the spread of HIV and AIDS in the US with special attention to the quality of information at hand and the kind of additional information that is needed; 2) identify critical populations and indicate objectives and tasks related to them; 3) describe existing research findings in the behavioral and social sciences that should be useful in planning and choosing among interventions designed to control the spread of HIV infection; 4) describe existing research on interventions intended to facilitate behavior changes and ways to evaluate their effectiveness; and 5) identify new research that should be undertaken in these areas. The 7 chapters of the resultant report are divided into 3 parts: Understanding the Spread of HIV Infection; Intervening to Limit the Spread of HIV Infection; and Impediments to Research and Intervention. Also included are 6 background papers. Among the recommendations of the Committee are: vigorous programs of basic social and behavioral research on human sexual behavior; availability of condoms and treatment for sexually transmitted diseases through local public health authorities; drug treatment upon request for intravenous drug users; trials of sterile needle programs; and anonymous HIV antibody testing with appropriate counseling on a voluntary basis.

Task-Related Differences in the Cuticular Hydrocarbon Composition of Harvester Ants, Pogonomyrmex barbatus

Colonies of the harvester ant, Pogonomyrmex barbatus, perform a variety of tasks. The behavior of an individual worker appears to depend on its recent history of brief contacts with ants of the same and other task groups. The purpose of this study was to determine whether task groups differ in cuticular hydrocarbon composition. We compared the cuticular hydrocarbon composition of ants collected under natural conditions as they performed one of three tasks: patrolling (locating food sources), foraging, or nest maintenance. Task groups differed significantly in the relative proportions of classes of hydrocarbon compounds, as well as in individual compounds. Relative to nest maintenance workers, foragers and patrollers had a higher proportion of straight-chain alkanes relative to monomethylalkanes, dimethylalkanes, and alkenes. There was no significant difference in the chain length of n-alkanes among the task groups. Foragers did not differ in hydrocarbon composition from patrollers. Colonies differed significantly from one another in hydrocarbon composition, but task groups differed in consistent ways from colony to colony, suggesting that the mechanism responsible for task-related hydrocarbon composition was the same in all colonies. P. barbatus workers switch tasks during their lifetimes, suggesting that cuticular hydrocarbon composition changes during adulthood as well. Nest maintenance workers are probably younger than foragers and patrollers and perform very little of their work outside of the nest. Task-related hydrocarbon differences detected here may be associated with worker age, and/or the abiotic characteristics (temperature, humidity, and ultraviolet light) of the interior and exterior work environments.

The series of consecutive cases as a device for assessing outcomes of intervention.

AN air of serving the common good clings to the process of reporting as general information the results of ones own extensive experience. Medicine enjoys a long tradition of such literature, and v...

Think and Explain with Statistics.

Think and Explain with Statistics. By L. E. Moses. ISBN 0 201 15619 9. Addison‐Wesley, New York, 1986. xii + 484 pp.

Statistical Concepts Fundamental to Investigations

Statistics may be defined as a body of concepts and methods for learning from experience — usually captured as counts or measurements from many separate instances showing individual variation. A li...

A note on the Wilcoxon-Mann-Whitney test for 2 x k ordered tables

Biological and medical investigations often use ordered categorical data. When two groups are to be compared and the data for the groups fall in three or more ordered categories, the Wilcoxon-Mann-Whitney (WMW) test uses information in the ordering to give a test that is usually powerful against shift alternatives. However, such applications of WMW often involve distributions for which extensive ties play an important role. Newly available computer programs for performing exact tests give deeper insights into the characteristics of the exact WMW distributions and the suitability of normal approximations. We offer practical advice, based on experience with published biomedical data sets and on numerical studies of hypothetical ordered tables, for the use of WMW and its normal approximations.

Effect of Weather on Infestation of Buildings by the Invasive Argentine Ant, Linepithema humile (Hymenoptera: Formicidae)

Abstract Weekly reports of the abundance of the Argentine ant, Linepithema humile, in 69 households for 18 mo (1/98–7/99) in the San Francisco Bay Area in northern California were compared with weather data. Ant abundance inside homes was highest in cold rainy weather, and there was a second smaller peak of ant abundance in hot dry weather. Pesticide use in the home decreased ant abundance, from one week to the next, only when ant abundance was extremely high.

One Sample Limits of Some Two-Sample Rank Tests

Abstract A composite hypothesis asserting some kind of equality about two distributions may be tested by use of a two-sample statistic. It is often true that if one sample size is allowed to become infinite in this statistic then it is interpretable as one for testing a simple hypothesis about the distribution furnishing the finite sample. (The simple hypothesis is furnished by the “infinite sample.”) Wilcoxons two-sample test studied in this way becomes a useful tool for certain kinds of problems. A rank test of Lehmanns reduces to either Fishers test for combining independent tests of significance or to one once proposed by Karl Pearson for the same purpose. Two natural one-sample limits of two-sample median tests are also presented.

Needed Data Expenditure for an Ambiguous Decision Problem

Abstract The amount worth spending to collect and analyze data depends on the uses of the data. We consider the determination of the optimal expenditure in some simple situations when only some aspects of the data use are known. In particular, we consider uses where an action is taken if a statistic exceeds a threshold τ, which is unknown at the time of data planning and collection (though its value will not depend on the value of the statistic). We analyze the sensitivity of the optimal expenditure to the a priori uncertainty in τ. For many decision problems, the optimal expenditure decreases with increasing uncertainty about τ, but we identify some uses for which the optimal expenditure increases with increasing uncertainty about τ. We also study the effects of other forms of ambiguity. Uncertainty about whether the data will be used typically decreases the optimal expenditure, as does uncertainty about the preferences represented in the decision making.