How many letters does the top answer for “establish after a calculation, investigation, experiment, survey, or study” have?

The most common answer is ascertain (9 letters).

Crossword clue: establish after a calculation, investigation, experiment, survey, or study

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

ascertain 9 letters wn-def

establish after a calculation, investigation, experiment, survey, or study

determine 9 letters wn-def

establish after a calculation, investigation, experiment, survey, or study