If the question is potentially embarrassing, you just tell the polled person to toss a coin (this being over the phone, the pollster cannot see the outcome), and to tell you the following:

• heads: yes
  
• tails: the true answer
  

If both answers are potentially embarrassing, you toss two coins and say:

• two heads: yes
  
• two tails: no
  
• one head and one tails: the true answer

"It's the statue, man, The Statue."