Fig. 2From: Validity of oral fluid test for Delta-9-tetrahydrocannabinol in drivers using the 2013 National Roadside Survey DataScatter Plots of THC Concentrations in Blood and Oral Fluid: (a) Original Scale and (b) Log-transformation (replacing zero values with 0.5), among Driver with Non-zero Values in either Blood or Oral Fluid (n = 500)Back to article page