Scientific methods are the way researchers collect and look at information. Good methods keep true to the information. Unfortunately, other methods can be used to skew the information in an attempt to support the researcher's own opinions. 

When researchers use good methods, their success rates are more reliable. If, on the other hand, they choose to only report on patients who do well after a procedure, their success rates probably won't give you a very realistic picture. 

Your doctor can be a good resource to help you figure out which sources to trust.