Department of Statistics, UCLA

This note analyzes ozone standard exceedance days in Bakersfield, Arvin, Oildale, and Shafter since 1989. We have plotted violations of both one-hour and eight-hour federal and state standards (data from CARB monitoring stations). We have also drawn linear regression lines to estimate trend. They show a modest long term improvement (around 20%) in violations of one-hour state standards, but generally a smaller increase in violations of eight-hour state standards. They also show larger improvement in urban Bakersfield than in the rural areas.