Left and middle panels: correlation plots of H₂CO integrated intensity ratio and kinetic temperature, respectively vs. line width. The error bars present the standard deviation of the weighted average for the integrated intensity ratio, 20% uncertainty in the line width and 30% uncertainty in the temperature. The best linear fit to the temperature data using the total least-square method (Vanderplas et al. 2012) is shown as the solid line. Right panel: The possible slope and intercept values with the 1, 2, and 3σ likelihood contours.