Convenience Sampling - A convenience sample is a group of  individuals who  are readily available to participate in a study. That is, the choice of the  sample  is  left completely to the convenience  of the  investigator. The cost  involve  in picking  up  the sample  is minimum and the cost of data collection  is also generally  low. For  example, the investigator wants to study  the demand  for the types of soft drinks. The interviewer  can go to some soft drinks shop and can  interview shopkeepers who happens  to come to  that particular shop and ask them questions regarding their choice  for soft drinks. Convenience sample suffers from excessive bias  from known and unknown source and also there  is no way  that the possible errors can be quantified. It  is good  for taking a quick opinion poll developing tools such as questionnaire or interview schedule and for preliminary study before developing an elaborate research proposal.