Wang Gang: It is confirmed that more than 80% of heroin users have a history of smoking marijuana  Such data seem to suggest that marijuana use will definitely lead to heroin use
Li Yan: Maybe marijuana use does lead to heroin use, but citing the statistics you mentioned to prove this is absurd, because 100% of heroin users have a history of drinking water
Provide evidence that the statistics Wang Gang used to support his conclusions were inaccurate.