Documentation self-reported measures

This report was significant in that it was the first epidemiological investigation of a military population with documented exposure to chemical agents or stimulants. The survey was conducted, however, 30 years after the exposure and with the exception of mortality records was limited to self-reported measures of health. 

Advances in measurement have freed the estimation of patient compliance from its long-standing dependence on methods easily manipulated by patients, whose reluctance to acknowledge poor compliance contributes to self-reporting bias, documented in many ways. The years 1986-1987 saw the introduction of chemical marker and electronic monitoring methods, which provide different but complementary estimates of the time history of dosing by ambulatory patients. These advances have been extensively reviewed (Feinstein, 1990 Pullar and Feely, 1990 Urquhart, 1990 Cramer and Spilker, 1991 Bond and Hussar, 1991 Vander Stichele, 1991 Kruse, 1992). The gist of both methods is as follows. 

As noted by the lOM, Although a wide range of possible exposures might be associated with adverse health outcomes in PGW veterans, data on these exposures are often not available when they are available, they are poorly documented. This lack of exposure information is at the core of the frustration in obtaining answers from epidemiological studies. Self-reports of exposure and estimates of individual exposure from unit level measurements will be subject to so much error that they are likely to yield inconclusive results and additional questions. ... 

The reports reviewed used consistent measures of exposure. Epidemiologieal studies of aviation accidents typically incorporate some measure of exposure (Li, 1994), such as flight hours documented during an investigation or self-reported flying hours. It is important to have a measure of exposure to interpret the relative risks associated with particular activities. In the reports on GA accident data reviewed during this project, the common measure of exposure was the total number of hours flown by GA per 100,000 hours. 

The center column of Figure 18.9 includes examples of the type of measurement tool or index that can measure the dimensions in the left column. Each of these measurement devices can be classified according to three basic sources of data direct observation, archival data (obtained from examining plant documents, memos, and government reports), and self report (such as verbal answers to interview questions or written reactions... 

Appraisal Document upkeep and filing QC measures in procurement Preparation of QC samples Self-assessments Participation in interlaboratory testing Continuing education Instrument calibration Data validation Data analysis Preparation of QA/QC reports to management... 

There are biases inherent in even the best historical time series. Measurement and sampling errors may affect reported trends, or the data collected may not measure the variables one set out to observe. Cultivating a sense of creative self-doubt - well developed among economic historians (see II, McCloskey, 1976, 444-445) - helps to minimize the uncertainties caused by the vagaries of historical data. In this spirit, the appendixes of this report provide documentation of our sources, assumptions, and analytical methods. We follow Simon Kuznets in his assertion that the most important characteristic of statistical data is, of course, their comparability - over time and space (II, Kuznets, 1951, 268). 

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