for, since I endeavored to discover the falsehood or incertitude of the propositions I examined, not by feeble conjectures, but by clear and certain reasonings, I met with nothing so doubtful as not to yield some conclusion of adequate certainty,〔【出典】日英対訳文・対応付けデータ（独立行政法人情報通信研究機構）〕"_DISCO03", "2593008"
and my first conjecture was that we had 'jumped' a grizzly.〔【出典】日英対訳文・対応付けデータ（独立行政法人情報通信研究機構）〕"_DAMNE", "2586315"
Then there are those who take about two minutes to fill in their brackets, making their choices based on their preferences of team mascots and nicknames, uniform colors, or by simply guessing."VOA-S062", "2514578"
a shot in the dark
hazard a conjecture
take ［make］ a blind guess
Her reply was a shot in the dark and the audience listened to it with confusion.