In our last post, we examined who is polled and how that impacts the credibility of the poll. If you'll remember, polls are more reliable when they are random from a defined population, like random digit telephone dialing. Poll results are less reliable when the poll participants select themselves, like Internet or TV call-in polls.
You'll also want to watch for when the poll occurred. According to pollster Claudia Deane, you should think "dead fish and relatives." You know, the 3-day rule? In the current political climate, some poll results can grow rancid even faster.
Polls can spoil quickly, for many reasons. Intervening events can change the way people think. Imagine polls taken on Friday, before the announcement of the financial melt down on Saturday. This event alone made a lot of people cranky. You can see how this change of mood could affect previous poll results.
Another big intervening event will be the debates. People could change their opinions after the debates, starting next Friday night, which is why poll results from this week might not be viable next week.
Of course, there will be post-debate polls. Even then, people change their minds after a couple of days. They watch the news, think about their current situations, and the story develops and evolves. In the Gore/Bush debates, many of the polls reported Gore as the winner the first day, but a few days later the polls reported a change of opinion toward Bush.
When you're looking at poll results, check out both the "methodology" box to see how they selected the sample, and when the poll occurred. Three days can be a good rule for large-scale polls, depending on the questions and any intervening events. Then ask yourself whether any significant events have occurred since the poll that would impact the results you are seeing.
Polls can be enlightening, if you know what they are actually telling you. If you think about who is participating and when the poll occurred, you are well on your way to putting these election polls into perspective. Are you ready to consider another important factor - the words of the question? Stay tuned.