In doing a mail survey one potential problem is nonresponse bias ...

[xclash]

In doing a mail survey one potential problem is nonresponse bias which refers to
 
  A) having too few surveys returned.
  B) sending the survey to a non-random sample.
  C) differences between those who return the survey and those who don't.
  D) having items on the survey that respondents leave blank.

Question 2

The experimental design that allows the greatest flexibility in setting the timing and level of the independent variable(s) is a ____ experiment.
 
  A) single-variable, single-level
  B) multiple-level
  C) single-variable, two-level
  D) baseline

[Brummell1998]

Answer to Question 1

C

Answer to Question 2

D