Repeated measures estimation of measurement bias for self-reported drug use with applications to the National Household Survey on Drug Abuse.

Direct estimates of response bias for self-reports of drug use in surveys require that essentially error free determinations of drug use be obtained for a subsample of survey respondents. The difficulty of obtaining determinations which are accurate enough for estimating validity is well-documented in the literature. Methods such as specimen (e.g., hair, urine) analysis, proxy reports, and the use of highly private and anonymous modes of interview all have to contend with error rates which may only be marginally lower than those of the parent survey. Thus, any methodology for direct validity estimation must rely to some extent on approximations and questionable assumptions. In this chapter, the authors consider a number of methods that rely solely on repeated measures data to assess response bias. Since the assumptions associated with these approaches do not require highly accurate second determinations they may be more easily satisfied in practice. One such method for bias estimation for dichotomous variables that is considered in some detail provides estimates of misclassification probabilities in the initial measurement without requiring that the second measure be accurate or even better than the first. This methodology does require, however, that two subpopulations exist which have different rates of prevalence but whose probabilities of false positive and false negative error are the same. The applicability of these methods for self-reported drug use are described and illustrated using data from the National Household Survey on Drug Abuse. In the discussion of the results, the importance of these methods for assessing the validity of self-reported drug use are examined.

Chemical and nutritional evaluation of two amaranth (Amaranthus cruentus)-based infant formulas.

The objective of this study was to calculate, prepare and evaluate the Protein Efficiency Ratio (P.E.R.) and Net Protein Utilization (N.P.U.) of two infant formulas made with amaranth (Amaranthus cruentus). Both formulas were formulated to match a previously developed and tested soy-oats infant formula. No significant differences were found between the three formulas with respect to corrected Protein Efficiency Ratio (P.E.R.) and Net Protein Utilization (N.P.U.) values. Only the product made with the 1-R fraction of amaranth was found to have a significantly lower P.E.R. than casein.

On the quality of reinterview data with application to the Current Population Survey.

"The [U.S.] Current Population Survey (CPS) reinterview sample consists of two subsamples: (a) a sample of CPS households is reinterviewed and the discrepancies between the reinterview responses and the original interview responses are reconciled for the purpose of obtaining more accurate responses..., and (b) a sample of CPS households, nonoverlapping with sample (a), is reinterviewed 'independently' of the original interview for the purpose of estimating simple response variance (SRV). In this article a model and estimation procedure are proposed for obtaining estimates of SRV from subsample (a) as well as the customary estimates of SRV from subsample (b).... Data from the CPS reinterview program for both subsamples (a) and (b) are analyzed both (1) to illustrate the methodology and (2) to check the validity of the CPS reinterview data. Our results indicate that data from subsample (a) are not consistent with the data from subsample (b) and provide convincing evidence that errors in subsample (a) are the source of the inconsistency."

Gonadotropin responsiveness to estrogens and low-level progesterone in the ovariectomized rhesus monkey.

When estrogen is administered to gonadectomized rhesus monkeys in sufficient quantity, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels are initially suppressed and gonadotropin secretion is subsequently augmented. This study was designed to examine the ability of various orally administered estrogens to elicit biphasic pituitary responses in adult castrate rhesus monkeys and to investigate the role of low-level progesterone in altering these responses. In an incomplete block design, 13 treatments were constructed: (E2): 0.5, 5.0, 50 micrograms/kg; (DES): 0.05, 0.5, 5.0 micrograms/kg; zearalenone (Z): 10, 100, 1000 micrograms/kg; or oil vehicle, each combined with progesterone. The remaining treatments (5.0, 0.5, and 100 micrograms/kg of E2, DES, and Z, respectively) did not include progesterone. During six intervals, E2, DES, or Z was administered orally on Days 1, 2, and 3 and blood was sampled on Days 0, 3, and 8 of each period. A main effect of estrogen treatment was observed for LH and FSH secretion on Day 3 but not Day 8. There was no main effect of progesterone alone on release of either LH or FSH on days 3 or 8, nor were significant carry-over effects of progesterone, E2, DES, or Z on LH or FSH concentration apparent by Day 8 of any treatment. However, progesterone synergized with E2 to suppress Day 3 LH levels. Conversely, DES and Z interacted with progesterone to facilitate LH secretion at this time.(ABSTRACT TRUNCATED AT 250 WORDS)

[Modeling matching error and its effect on estimates of census coverage error].

"In this paper, we propose a model for investigating the effect of matching error on the estimators of census undercount and illustrate its use for the 1990 [U.S.] census undercount evaluation program. The mean square error [MSE] of the dual system estimator is derived under the proposed model and the components of MSE arising from matching error are defined and explained. Under the assumed model, the effect of matching error on the MSE of the estimator of census undercount is investigated. Finally, a methodology for employing the model for the optimal design of matching error evaluation studies will be illustrated and the form of the estimators will be given."