While a lot of people would say that the law of averages would say that flipping a coin means there will be five heads and five tails. Anyone who has flipped coins know this isn't necessarily true. However, things do even out in the long run. In ten flips of the coin, we would not be surprised to get seven heads and three tails. However, we would be quite surpised to flip a thousand times and get seven hundred heads and three hundred tails.
Sometimes the probablilities will sometimes change because circumstances change. We expect coins to fall 50-50 regardless what year we do the flipping. The average life span though has changed through the years.
How about home field advantage for a major league baseball team. Things have certainly changed there. A hundred years ago there were no night games, all the players were white, and spitballs were legal. Fenway Park and Wrigley Field were brand new stadiums. It wouldn't be surprising if home field advantage, if there really is such a thing, didn't change some through the years. Check out the home field winning percentage by decade. (From www.baseballprospectus.com/)
1900-1909 53.3%
1910-1919 54.0%
1920-1929 54.3%
1930-1939 55.3%
1940-1949 54.4%
1950-1959 53.9%
1960-1969 54.0%
1970-1979 53.8%
1980-1989 54.1%
1990-1999 53.5%
2000-2009 54.2%
Maybe even more striking (pun!) is to look at figures rounded to the nearest percentage.
1900-1909 53%
1910-1919 54%
1920-1929 54%
1930-1939 55%
1940-1949 54%
1950-1959 54%
1960-1969 54%
1970-1979 54%
1980-1989 54%
1990-1999 54%
2000-2009 54%
A good intro to this might be to have students share if they think if there is such a thing as home field advantage, what it might be, and would it have changed in the past century.
