Update 3: Data & Initial Raster Results

I will now be looking at four different variables in order to determine the lowest and highest risk areas for asthma sufferers in the state of California: (1) Percentage of days ozone exceeded the national average, (2) Income, (3) Population Density, (4) Hospitals.  I will convert each of these shapefiles to rasters so that I can perform a spatial raster analysis using a weighted overlay.  After converting each shapefile to a raster, they will be reclassified for favorable criteria.  Because the ozone data that I had imported from excel are points rather than polygons, I performed a spatial join between ozone exceedances and counties and then converted the county polygon that now contains the ozone data to a raster.