The Kyoto Protocol was signed in 1997, and required countries to start reducing their carbon emissions. The protocol became enforceable in February 2005. In 2004, the mean CO2 emission was 4.87 metric tons per capita. In 2010, the CO2 emissions for a random sample of 45 countries were collected. Is there enough evidence to show that the mean CO2 emission is different in 2010 than in 2004