may serve as suggestions for future analyses and reports of the Ranch Hand data and those of similar groups.


The comments that follow focus on the report dealing with reproductive outcomes (AFHS, 1992). The committee feels, however, that many of its observations have somewhat broader applicability to other aspects of the Ranch Hand study as well.

Tabular Presentation of Results

One general concern is that many of the tables and analyses are confusing and inadequately documented. The definitions of column and row labels in the tables relied on prior text so that the tables do not stand alone. There are p-values presented without adequate descriptions of the specific hypotheses being tested. Although a thorough reading of the methodology section (Chapter 1) provides the required information, interpretation of the tables would be facilitated by the inclusion of better "stand-alone" documentation in the form of footnotes and expanded row and column headings. Overall, the committee believes that some clarification, some simplification, and more emphasis on estimates of effect than on p-values would help the researchers communicate their important findings and would facilitate the appropriate peer review of this work.

Similarly, the committee feels that there is an overreliance on p-values in place of simple measures of effect such as relative risks. The executive summary, in particular, contains essentially none of the relevant quantitative data.

Exploration of an Overall Effect

A more specific concern involves the text on page i, describing overall differences between Ranch Hands and control groups. Initial findings, using unverified end points, showed that when looking at births occurring prior to the Ranch Hands' experience in Southeast Asia (pre-SEA), the comparison group had slightly elevated rates of adverse outcomes. When looking at post-SEA births, the reverse was true; that is, the rate of adverse birth outcomes was higher for Ranch hands. The 1992 report states that subsequent analyses of verified end points confirmed these findings, but the committee could find only one table reporting the findings, and this table did not provide any information specific to particular types of birth defects or several other outcomes.

The data in table 1-16 suggest that some aspect of Ranch Hand service

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