ANECDOTAL EVIDENCE

What is "anecdotal evidence"?
 

The term "anecdote" means a story, a tale, or even a legend.  But in our context, the term "anecdotal" primarily means unreliable or subjective.  What would make data or evidence unreliable or subjective? 
 

1.  Using observations that do not properly represent the entire set of
     possible observations.

     Example:  Formulating a hypothesis for why students find Geology
                     100 difficult based on the reactions of only those students
                     who come to see me during office hours.
 

2.  Using only those observations that reflect someone's point of view,
     while other data are ignored.

     Example:  If a cigarette company hypothesized that smoking is good
                      for your health based on the medical histories of only those
                      smokers who have lived to be more than 75 years old.