Left: Correlation derived from bootstrapping the signal by individual sources; same as Fig. 6, but with the color stretch adjusted to the middle plot. Middle: Correlation derived from bootstrapping the signal in 1 deg² tiles. The upper-left corners show the correlations from LAD regression. The lower-right corners show the correlations from using the weighted mean. Right: Comparison of the errors obtained from bootstrapping sources (LAD: solid blue; mean: solid red) and bootstrapping 1 deg² tiles (LAD: dashed blue; mean: dashed red).