By design, bit perfect reading  of an audio CD is not guaranteed.
    This is inherent to the  Red Book audio standard. 
    See the ripping section for  more detail.
AccurateRip is an internet  database.
    For each ripped track, a  checksum is calculated and submitted to this database.
    The moment a single bit  changes, the checksum will change too.
    If you submit your rip to  this database the answer is a confidence report.
    Confidence because we cannot  tell for sure if a rip is the ‘right’ one.
Different users rip the same  CD.
    As far as the content is  concerned, it is the same CD.
    However, physical it is a  different CD and it scratches are unique for sure!
    The optical drive are  different too in a likewise manner.
It is not likely that there is a systematically error in the ripping process.
A systematically error would mean that each  time a track is ripped exactly the same sector will generate the same read  error on each CD on each optical drive.
    If this was the case, we might write a  program to correct it.
  It is likely that the errors  are random. Sometimes somewhere a read will not be bit perfect and this will  happen with a specific CD on a specific optical drive.
    The logical consequence: if  the number of users reporting the same checksum increase, the higher the likelihood  that this the ‘right’ rip.
As with all statistical approaches, there is no absolute truth, there is likelihood.
However, if your rips are identical with the rips of others, it is highly likely that you do have the right rip.
You cannot buy AccurateRip.
    Either your ripper supports  it or it doesn’t
    The AccurateRip website gives  an overview of ripping programs using it.
AccurateRip - website