Abstruc:I n inany situations one wishes to fit a piecewise regression model which enables one to obtain estimates of the join points as well as the slopes and intercepts of the fitted submodels. This study developes a technique for fitting piecewise models to date, which contain meaaurement error in a n independent variable. The technique developed here combines the HUDSON (1966) procedure for estimating parameters in piecewise regression and the WALD (1940) Grouping Technique which obviates the problem of measurement error.If one assume8 some knowledge of the position of the join point in relation to the data, methodology has been developed to estimate the parameters and study the asymptotic properties of the means and variances of the parameter estimates. However, in the more realistic case, when additional knowledge is limited, it is only possible to obtain the parameter estimates using a n iterative technique (TEETER, 1982).The general technique for obtaining the join point estimate in the presence of measurement error is presented here and an example is given using dat8 on women's basal body temperature during menstrual cycles.
Some investigations of IUD use have demonstrated impaired ability to become pregnant after removal, while others have not. None of these studies, however, have adequately considered such potentially influencing variables as age and a history of pelvic inflammatory disease (PID). To study the effect of length of IUD use, IUD type and the modifying influences of age and PID history on time required to conceive, we followed women trying to become pregnant after removal of their IUD. Five hundred forty women in Ljubljana, Yugoslavia who were first fitted with an IUD between 1964 and 1972 and had their IUD removed in order to become pregnant were followed through 1980. We found no relationship between the duration of IUD use or type of IUD used, but increasing age and a history of PID each decreased the monthly probability of conception. These findings, along with other recent work, indicate that IUDs are a safe and efficacious contraceptive for women at low risk for sexually transmitted diseases.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.