In a mail survey, 500 questionnaires were sent out but only 200 ...

[K@]

In a mail survey, 500 questionnaires were sent out but only 200 were returned.
 a. This survey has random sampling error.
  b. This survey has a response bias.
  c. This survey has nonresponse error.
  d. This survey suffers from deliberate falsification.
  e. None of these are correct.

Question 2

Abdul downloads the hottest new mobile game, Crash of Clans 106 . When he installs the game, he checks a box to indicate that he would like to receive promotional emails from the game's developers. Later that day, he receives an email in which he has to click another link to verify his willingness to receive further emails. This process is an example of:
 a. opt-out.
  b. opt-in.
  c. double opt-in.
  d. confirmed opt-in.

[succesfull]

Answer to Question 1

c

Answer to Question 2

c

[K@]

Excellent

[Bigfoot1984]

Gracias!