Given a 10-step online survey (mostly yes/no radio buttons), where is it best to ask for the users' personal data e.g. name, age, contact details?
My intuition says putting it at the end will yield better completion rates, as users have already invested time in filling out the "easier" and less personally involved part.
What factors should be considered? Are there reasons to ask for users' personal data at the beginning instead?
Should placement be different if the users' personal data input is optional?