N-estimation from retrospectively ascertained events with applications to AIDS
Related Experiment Video
Updated: Sep 22, 2026

An Affordable HIV-1 Drug Resistance Monitoring Method for Resource Limited Settings
Published on: March 30, 2014
1Department of Biostatistics, Johns Hopkins University, School of Hygiene and Public Health, Baltimore, Maryland 21205.
Abstract:
It is a common sampling scheme in retrospective studies that the data set includes only individuals who satisfy a certain sampling criterion. In this paper we consider the situation when the sampling criterion is a specified event, and assume that an earlier event can be retrospectively identified given the occurrence of the specified event. A semiparametric method, which is a compromise between nonparametric and parametric methods, is employed for the estimation of the expected number of the specified events (namely, the N-estimation) occurring in arbitrarily given intervals. A number of statistical properties of the estimates are developed. Due to the limitation of semiparametric models, our estimates should be regarded as conservative estimates since in general they underestimate the actual number of the specified events. This type of limitation, however, cannot be avoided with nonparametric or semiparametric models. Applications to acquired immunodeficiency syndrome (AIDS) cases are considered. The blood transfusion AIDS cases reported to the Centers for Disease Control are analyzed in detail.
More Related Videos
10:46A Method of Trigonometric Modelling of Seasonal Variation Demonstrated with Multiple Sclerosis Relapse Data
Published on: December 9, 2015
10:29Quantitative Structure-Activity Relationship, Activity Prediction, and Molecular Dynamics of Non-nucleotide Reverse Transcriptase Inhibitors
Published on: May 9, 2025
Related Concept Videos
Retrovirus Life Cycles
Types of Biopharmaceutical Studies: Controlled and Non-Controlled Approaches
Non-controlled studies, commonly employed for initial exploration, lack a control group, rendering them susceptible to biases and external influences. In contrast, controlled...
Introduction To Survival Analysis
The primary goal of survival analysis is to estimate survival time—the time until a...
Actuarial Approach
Consider the example of a high-risk surgical procedure with significant early-stage mortality. A two-year clinical study is conducted,...
Kaplan-Meier Approach
Assumptions of Survival Analysis