Sampling hidden populations is challenging due to the lack of convenience statistical frames. Since most populations exposed to special diseases are hidden and hard to reach, sampling methods that produce representative and efficient samples from the populations have become a study subject for researches all over the world. Because of the unknown probability of selecting samples in conventional...

Objectives: Study of hidden populations such as Injection Drug Users (IDU) due to their exposing to high risk diseases and their roll in public health is very crucial. Conventional statistical methods for sampling these populations are not applicable because of the restrictions these populations are faced. Despite the introduction of respondent driven sampling as a successful method for samplin...