1. Under Color Picker tool, there is an option "Sample Average" (with tooltip "Use averaged color value from nearby pixels"), for which the manual says :
"The Radius slider adjusts the size of the square area that is used to determine an average color for the final selection. When you keep clicking the layer, the mouse pointer shows the size of the square or radius."
2. Under color picker tool, there is another option "Sample Merged" (with tooltip "Use merged color value from all composited visible layers"), for which the same manual says:
"When enabled, the Sample Merged checkbox will take color information as a composite from all the visible layers. Further information regarding Sample Merge is available in the glossary entry, Sample Merge."
3. Clicking Menu → Colors → Info → Export Histogram... → the popup menu contains an option "Sample Average" (no tooltip here, except repeating the command text), for which the manual says :
"If Sample Average is activated, the histogram will be generated for an image obtained by merging all visible layers. Otherwise, the histogram will only consider the current layer."
Question: shouldn't be "Sample Merged" in 3. too ?