A study of an association between which ear is used for cell phone calls and whether the subject is left-handed or right-handed began with a survey e-mailed to 5000 people belonging to an otology online group, and 717 surveys were returned. (Otology relates to the ear and hearing.) What percentage of the 5000 surveys were returned? Does that response rate appear to be low? In general, what is a problem with a very low response rate?

Of the 5000 surveys, % were returned. This response rate to be low.

What is a problem with a very low response rate?

a. It indicates a lack of blinding which creates a serious potential for getting a biased sample.
b. It does not allow for sufficient replication to produce a random sample.
c. It creates a serious potential for getting a biased sample that consists of those with a special interest in the topic.
d. It creates a serious potential for confounding which creates a serious potential for erroneous conclusions.