nate silver

An Election: Heads vs. Tails

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Yesterday during a tangent in my Algebra 2 class I realized how little understanding my students had about the voting process as well as how predictions are made and how, when, and why networks announce winners without all of the votes counted.

Today, I ran an activity that pitted Heads vs. Tails. Each student received a penny and flipped the coin to determine their vote: Heads or Tails.  The class consisted of 19 students.

In our first election, we strictly counted votes- a popular election.  Tails beat heads 10-9.

In our second election (everyone re-flipped their coin), the girls announced first: tails 6 and heads 5.  I asked our students, what do we EXPECT to happen with the remaining 8 votes?  Assuming fair coins, we expect 4 for heads and 4 for tails.  So if we had to bet, would we bet that heads would win or tails? Since tails already had a 1 vote lead, tails was most likely to win.  In fact, the scenario most likely to result in a win for heads was 5 heads and 3 tails.  This was not a probability class, but with some basic concepts we could have given percentages to each outcome.

Back to this specific election:  With only the girls reporting, the vote was 6 for tails and 5 for heads.  I asked one boy to announce his result.  He flipped tails, so the vote count was 7 for tails and 5 for heads.  I declared, “I am ready to call the election for tails!”  The students protested; there were 7 students still left to vote.  Could heads have come back and won?  Yes, but this was unlikely since 5 of the 7 remaining flips would need to be heads.  We counted the votes and tails won 10-9 (4 of the 7 remaining flips went to heads).  I did not have a specific percentage in mind when I “called” the election (the real chance when I declared tails victorious was around 75%, but I wanted to make a point).  We discussed how, when, why (and the implications) newspapers and television stations “call elections.”

In our third election, I told the class that the front row (5 students) always voted heads and were going to vote for heads again.  With 14 students left to flip, I said that I had enough information to call the election and was sure heads would win.  Again, with the likelihood around 75% that heads would win, there was a decent chance tails could come back, but again, I was making a point.  We then discussed how this activity mirrored the Electoral College with states like California consistently voting democrat.

Finally (and I did not have time to do this election), I was going to weight each row differently.  The first row would vote and their winner would receive 4 votes, the winner of the second row would receive 3 votes, the 3rd row two votes and the back row one vote.  I was going to have each row announce in order 1-4, then redo this system with the back row announcing first.

Please leave a comment if you have any ideas on improving this exercise or need any help implementing it in your class.