Figure 4: A 2005 comparison of nutrient concentrations measured in dilution series of standards (Nitrate+Nitrite, Silicate, Phosphate) or in water samples collected in San Francisco Bay (Ammonium) by two laboratories.
From: Water quality measurements in San Francisco Bay by the U.S. Geological Survey, 1969–2015

USGS Menlo Park (USGS-MP) and San Francisco State University (SFSU). Linear regressions include an intercept if it was statistically significant. Adjusted R2 and Residual Standard Errors (RSE) are shown for each regression.