It's like a survey on lets say , "conscription" The reseachers and those who they work for are after a particular answer. So they will draw up a survey. And the questions will read like this.:
do you think there is high crime in this country?
do you think that youth crime is up?
do you believe there should be more job oppotunities for the youth.
do you believe children need more discipline?
do you believe the world is a more dangerous place today than when you were a child?
Do you believe in gun control?
do you believe those in the armed forces are dedicated and discaplined people?
do you believe that you are patriotic?
do you believe there should be compulsory National service for the youth of today?
Now most would answer yes to all of those
then you put in the clincher question. "Do you believe in conscription?"
You see people dont' want to say no to the last because they just said yes to the other leading questions and fear they may look stupid .
So next thing you know conscription becomes law.
and that's how it's done.
If you were to ask someone in the street what religion they are they will tell you more likely what they are baptised as ..........................but no one is going to ask if they practise it because that won't give the answer the surveyer is after.