I'm taking an online course in Usability Surveys.
Both of these seem to be about missing some group from the sample. The example in the course is: You are surveying people about a new HR Form. You leave out the janitors. That's a sampling error. You email the survey but folks without email don't get it, that's a Coverage Error.
But another definition I found suggests that sampling error is more like "the sample you surveyed wasn't large enough" (statistically valid).
Which definitions should I use for coverage and sampling errors?