Why Presidential Polls Vary So Much

A Fox News poll has John McCain down just 3 points in the polls, stating: "The race has tightened with Barack Obama now leading John McCain by 47 percent to 44 percent among likely voters."

A CBS News/New York Times poll has Barack Obama up by 11 percentage points, 52 to 41, among likely voters nationwide. Earlier this week there were polls suggesting the race was too close to call. Some variations result from whether likely voters are polled vs. any, um, Joe. The way questions are phrased has a big effect, too. In the end, polls are typically flawed, one expert says. Among the problems: People without land lines are often excluded, and people change their minds.

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Robert Roy Britt

Robert is an independent health and science journalist and writer based in Phoenix, Arizona. He is a former editor-in-chief of Live Science with over 20 years of experience as a reporter and editor. He has worked on websites such as Space.com and Tom's Guide, and is a contributor on Medium, covering how we age and how to optimize the mind and body through time. He has a journalism degree from Humboldt State University in California.