Archive for April, 2014

Shared Names and Voter Fraud

Posted: April 6, 2014 in analysis contributor streiff wrote an analysis of a Fox News story about database matching of North Carolina’s voter roles.  The original story, while somewhat alarmist, at least acknowledges that the analysis is preliminary at best. What North Carolina did was compare a complete list of everyone who voted in NC in 2012 to a list of voters in 28 other states.   35,750 voters matched first name, last name, and birthdate.  765 voters also matched the last 4 digits of their social security number. The Fox News article points out that these aren’t guaranteed cases of voter fraud, but streiff ignores this, with his headline “Rampant Vote Fraud Uncovered In North Carolina”, and comments like this:

This is not a minor problem, this is an industry. Under a most favorable scenario one has to expect the overwhelming majority of the voters matching name and date of birth are the same person.

I don’t think we can accept that claim without some analysis.  The match on matching in large groups is a funny, and most people don’t judge it very well.

Birthdays In A Room

The classic example of this is to ask “How many people need to be in a room before there is a 50% chance that two of them share a birthday?”.  Most people think that, with 365 days to choose from, it would need to be in the hundreds. The actual answer is 23.  The first person to enter the room can have any birthday.  The second person has one day they cannot have.  The third has two, and so on.  While the chance for each person colliding with someone else as they enter the room is low, the cumulative chance that every person will dodge every other person shrinks faster than most people think. (more…)