The indoor air quality (the concentration of particles less than 2.5 microns in diameter) in 15 bars, restaurants, and other public venues in Louisville was measured prior to the introduction of new...

The indoor air quality (the concentration of particles less than 2.5 microns in diameter) in 15 bars, restaurants, and other public venues in Louisville was measured prior to the introduction of new smoking regulations. Two months after all public venues were required to be smoke-free, the air quality was measured again. The data (in mg/m3 ) are given in the following table.