What kind of error Each of the following is a source of erro

What kind of error? Each of the following is a source of error in a sample survey. Label each as sampling error or nonsampling error, and explain your answers. The telephone directory is used as a sampling frame. The subject cannot be contacted in five calls. Interviewers choose people on the street to interview.

Solution

a)Non-sampling error. Because the whole telephone directory is chosen as sample frame.
b)Sampling error. Because the subject is specific in the sample.
c)Non-Sampling error. Because sample here is the people on streets not few selected ones.