Lusardi, Tufano and TNS Global asked 1000 U.S. residents the following question:

You purchase an appliance which costs $1,000. To pay for this appliance, you are given the following two options:

a) Pay 12 monthly installments of $100 each;
b) Borrow at a 20% annual interest rate and pay back $1,200 a year from now.

Which is the more advantageous offer?

Result:

Here are all the results from the survey. Unbelievable. The questioning was done over the phone which could distort the results a bit but it's nevertheless a disaster.