You just read a study which reports that marijuana use leads to heroin addiction. after a careful examination of the literature, you are unable to find any other researcher who has been able to duplicate these results. you may conclude that this study lacks:

This study demonstrates a lack of reliability.

Reliability basically refers to the ability of a test or measurement tool to produce consistent results that can be replicated. If a test or tool gives the same result repeatedly, it is considered to be reliable. In this instance, since the finding "marijuana use leads to heroin addiction" is not found elsewhere, the study lacks reliability.