A +/- 1.80 is a 3.60 range. From - 1.80 to + 1.80. But I may be confused about the english term to describe it. Sorry. Do you think the probabilities I gave are wrong, why? I gave them grosso modo, of course. I don't think they are wrong. I only want to know what is the logic behind their atm option pricing . Like a manufacturer that sells his product knows exactly what are the cost and what are his profit margin . Why the market makers, manufacturers, are pricing the options like they do. It is not a question to win, it is only to think.
Below is plus/minus over 1% on expiry day - not including today. SPY ATM straddles/strangles entered one day before expiry would end up losing over the year.
For last year's expirations, 25% of the time, the SPY move up or down more than 90 cents, This year it's 72% As for accuracy, I am right 92% of the time and the remaining 27% of the time, I have no clue