The Margin of Error?

I’ve just had my fourth phone call for a political poll. All of them in the dinner hour. One I just refused to handle and two I put on hold while I answered the door and when I got back they’d gone. Funny, that.

This last call I answered as well as I could about how I’d voted last time and various things. Then I found myself saying No to a series of questions about voting in Taranaki. I asked why was I expected to know about Taranaki and, after a lengthy pause—oh, dear, I’m sorry, we’ve made a mistake.

I was more than slightly concerned about this kind of “mistake” so I asked for a chat with the duty supervisor. Again, an apology was forthcoming and then I was assured that my responses would be discarded. That didn’t impress me too much, either.

What reliance can we place on results when the interviewers pick up the wrong question sheet or don’t know where their respondents live and then discard certain results on a cavalier basis?