People who are cannot be contacted or who refuse to participate ...

[big1devin]

People who are cannot be contacted or who refuse to participate in a survey are called ___________________ _.
 Fill in the blank(s) with correct word

Question 2

When the people who answer a mail survey are different in important ways (e.g., income level) from the people who did not answer the survey, the survey is said to have ___________________ _ error.
 Fill in the blank(s) with correct word

[dmurph1496]

Answer to Question 1

nonrespondents

Answer to Question 2

nonresponse

[big1devin]

TYSM

[Sarahjh]

Thanks for the timely response, appreciate it