AEA "Survey"

"Self Selection" is a potential problem with virtually all polling, and it was the first thought I had when I heard about AEA announcing the results of a "survey" of teachers about reopening classrooms during Covid19.

The results of the "survey" are HERE.

I could not find any information about how the AEA survey was conducted, other than this reference:

"In mid-July, AEA conducted a survey with questions specific to the reopening of schools for the upcoming school year amid COVID-19. The survey, which ran July 13-15, had almost 41,000 participants who voiced their concerns." 

Self-selection makes determination of causation more difficult. For example, when attempting to assess the effect of a test preparation course in increasing participant's test scores, significantly higher test scores might be observed among students who choose to participate in the preparation course itself. Due to self-selection, there may be a number of differences between the people who choose to take the course and those who choose not to, such as motivation, socioeconomic status, or prior test-taking experience. Due to self-selection according to such factors, a significant difference in mean test scores could be observed between the two populations independent of any ability of the course to effect higher test scores. An outcome might be that those who elect to do the preparation course would have achieved higher scores in the actual test anyway. If the study measures an improvement in absolute test scores due to participation in the preparation course, they may be skewed to show a higher effect. A relative measure of 'improvement' might improve the reliability of the study somewhat, but only partially.
Self-selection bias causes problems for research about programs or products. In particular, self-selection affects evaluation of whether or not a given program has some effect, and complicates interpretation of market research.