Estimating the proportion of non-heterosexuals in Taiwan using Christofides' randomized response model: A comparison of different estimation methods.

In social research, investigating sensitive, highly personal or embarrassing issues by means of standard survey techniques based on direct questioning leads to refusals to answer or false responses which, generally, flaw the validity of the analyses and produce incorrect inferences. To correct biases induced by nonresponse or underreporting of sensitive matters, Warner (1965) introduced an indirect questioning approach, known as the randomized response technique, which allows researchers to estimate the proportion of individuals with sensitive attributes or behaviors, while ensuring respondents' privacy protection. In this article, we consider the randomized response model proposed by Christofides (2003) and, through a simulation and an empirical study, compare different estimation methods for the prevalence of a sensitive attribute. Specifically, we discuss how the model has been implemented in a pilot study to collect data and derive maximum likelihood and Bayesian estimates for the proportion of non-heterosexuals aged 20 years or older for the Taiwanese population and for some subgroups of it by sex and age. Our analysis, and in particular the Bayesian approach, seems to meet the expectation of social researchers and experts of sexual behaviors. In fact, the produced estimates are higher than official findings in Taiwan obtained by direct questioning in face-to-face interviews and provide a more reliable picture of sexual identity in the country. Moreover, Bayesian estimates appear more accurate than those produced by the method of moment and the maximum likelihood method.

Estimates of Lifetime Extradyadic Sex Using a Hybrid of Randomized Response Technique and Crosswise Design.

The prevalence of extradyadic sex (EDS) tends to be underestimated due to underreporting in national surveys, which use direct questioning. Self-administered questionnaires can reduce this response bias but may cause the anxiety of privacy exposure. Randomized Response Technique (RRT) can ensure participants' confidentiality under the randomized design of indirect questions to and was found to yield more valid estimates of sexual or other sensitive behaviors than direct questions. This study estimated the EDS rate among Taiwanese aged 18 years and over, using a hybrid of Randomized Response Technique and Crosswise Design (RRTCD) and the Weighted Conditional Likelihood (WCL) estimator. The data analyzed were from the 2012 Taiwan Social Change Survey, in which the answer to the innocuous question from the unrelated-question RRT of Greenberg, Abul-Ela, Simmons, and Horvitz (1969) was obtained indirectly from a demographic question related to the innocuous question. This RRTCD provided more information on the innocuous question to effectively improve the efficiency of the unrelated-question RRT of Greenberg et al. The WCL estimator was found to be more efficient than the Greenberg et al. estimator for estimating the EDS rate in terms of smaller standard errors and smaller differences in the levels of EDS across sociodemographics and extramarital-sex attitudes. Similar to those suggested in the literature, the estimated rates of EDS in two subsamples were higher among men, homosexuals, those who have or had wages, and those who accepted extramarital sex. The levels of EDS varying with sociodemographics were different between the married and the unmarried.

An alternative to unrelated randomized response techniques with logistic regression analysis.

The randomized response technique (RRT) is an important tool that is commonly used to protect a respondent's privacy and avoid biased answers in surveys on sensitive issues. In this work, we consider the joint use of the unrelated-question RRT of Greenberg et al. (J Am Stat Assoc 64:520-539, 1969) and the related-question RRT of Warner (J Am Stat Assoc 60:63-69, 1965) dealing with the issue of an innocuous question from the unrelated-question RRT. Unlike the existing unrelated-question RRT of Greenberg et al. (1969), the approach can provide more information on the innocuous question by using the related-question RRT of Warner (1965) to effectively improve the efficiency of the maximum likelihood estimator of Scheers and Dayton (J Am Stat Assoc 83:969-974, 1988). We can then estimate the prevalence of the sensitive characteristic by using logistic regression. In this new design, we propose the transformation method and provide large-sample properties. From the case of two survey studies, an extramarital relationship study and a cable TV study, we develop the joint conditional likelihood method. As part of this research, we conduct a simulation study of the relative efficiencies of the proposed methods. Furthermore, we use the two survey studies to compare the analysis results under different scenarios.

Semiparametric methods in the proportional odds model for ordinal response data with missing covariates.

We consider the estimation problem of a proportional odds model with missing covariates. Based on the validation and nonvalidation data sets, we propose a joint conditional method that is an extension of Wang et al. (2002, Statistica Sinica 12, 555-574). The proposed method is semiparametric since it requires neither an additional model for the missingness mechanism, nor the specification of the conditional distribution of missing covariates given observed variables. Under the assumption that the observed covariates and the surrogate variable are categorical, we derived the large sample property. The simulation studies show that in various situations, the joint conditional method is more efficient than the conditional estimation method and weighted method. We also use a real data set that came from a survey of cable TV satisfaction to illustrate the approaches.

Characterization of cyclodextrin glycosyltransferase of the same gene expressed from Bacillus macerans, Bacillus subtilis, and Escherichia coli.

The plasmid pHG contains a cyclodextrin glycosyltransferase (CGTase) gene (cgt) derived from Bacillus macerans. Two transformants, Bacillus subtilis (pHG) and Escherichia coli (pHG), were found to produce CGTases with the same primary structure as the enzyme from B. macerans. However, the beta-cyclodextrin coupling activity of the CGTase from E. coli (pHG) was 14-fold higher than that of the enzymes from the other strains. By contrast, no differences in alpha-cyclodextrin coupling activities were observed among these CGTases. CGTase from E. coli (pHG) was found to be less thermostable than the other CGTases. When the CGTase produced by B. subtilis was treated with increasing urea concentrations (10-1000 mM) to promote increasing degrees of protein unfolding, a bell-shaped beta-cyclodextrin coupling activity profile was obtained. Subtle differences in the conformation of the CGTase produced by E. coli are therefore proposed to be responsible for the markedly increased beta-cyclodextrin coupling activity of this enzyme.

Cranial-base morphology in children with class III malocclusion.

The association between cranial-base morphology and Class III malocclusion is not fully understood. The purpose of this study was to investigate the morphologic characteristics of the cranial base in children with Class III malocclusion. Lateral cephalograms from 100 children with Class III malocclusion were compared with those from 100 subjects with normal occlusion. Ten landmarks on the cranial base were identified and digitized. Cephalometric assessment using seven angular and 18 linear measurements was performed by univariate and multivariate analyses. The results revealed that the greatest between-group differences occurred in the posterior cranial-base region. It was concluded that shortening and angular bending of the cranial base, and a diminished angle between the cranial base and mandibular ramus, may lead to Class III malocclusion associated with Class III facial morphology. The association between cranial-base morphology and other types of malocclusion needs clarification. Further study of regional changes in the cranial base, with geometric morphometric analysis, is warranted.