Round each number to the nearest
ten, and then add to find an
estimated sum.
424 + 19 =

424 is rounded to 420
19 is rounded to 20
420+19 is equal to 440

Question: An airline wants to survey customers about their overall satisfaction. They take a random sample of 1,000 customers who have flown in the past month and email them a survey. The email also offers those who complete the survey a  25 gift card that can be used almost anywhere.

Which of these is the best example of non-bias response ?

A.