Option Price

Discussion in 'Options' started by raf_bcn, May 8, 2018.

  1. raf_bcn

    raf_bcn

    Hi
    An options newbie question.

    Imagine this scenario
    Underlying at 266 and 1 Dte.
    The atm call is priced at 0.90 , What does it mean? Why the sellers are asking that price ? It seems that the sellers thinks the underlying will go as maximum to 266.90 until expiration.
    If the volatility remains equal. Is that right ? otherwise they would not be selling.
    _What is the probability of the underlying close above 266.90 ? Why are they satisfied with that probability?

    I would like to know what is the logic behind that price.
    thank you.
     
  2. Robert Morse

    Robert Morse Sponsor

    If:
    Underlying at 266
    1 day left
    Strike price of 266? If it is the 266 and the put is also ~ 0.90, that makes the straddle ~1.80. That means "the market" is is pricing in a range of 1.80 for one day. That is around 0.676%. You are only looking at one side, the model implies you hedge. If you buy the call for $0.90, some one else will sell that call and hegde with buying around 50 shares per options.

    I'll leave the probability up to you as to a close at or above 266.90. To get that, you would have to model the 266.90 call and look at the that delta.

    Bob
     
    tommcginnis likes this.
  3. tommcginnis

    tommcginnis

    Or, another way to put it, that the 90¢ pricing expects a 50|50 shot of $1.80 on the call side, alone, bringing the price to $267.80. That $1.80 movement becomes the target, the 50|50 odds bringing it to an instantaneous value of E(V) = $1.80*50% = $0.90....

    A different way to say the same thing.
     
    • SPY at 266.70
    • SPY May09 2018 266.500 call - ask at $0.85
    • SPY May09 2018 266.500 put - ask at $0.79
    • Expires tomorrow
     
  4. spindr0

    spindr0

    Look at the delta of the $267 call then fudge it down by 10%. It will be close enough for civil service work :)

    If you prefer something more accurate, toss all of the option variables into an option pricing model, using a hypothetical $266.90 call
     


  5. Bid on the SPY May09 2018 266.500 call is $3.06
     
  6. raf_bcn

    raf_bcn

    Hi


    So, call 0.90 + put 0.90 = 1.80 The market is pricing in a range of +/- 1.80 , this is a 3.60 range. A 66 % probability, 1 sd, that the underlying will be between that two points at expiration with actual iv. All depends on the iv the market makers determine for that day.
    One day I will ask how they arrive to that consensus.

    The probability of the underlying closing above 1 sd, + 1.80 is (1-0.66)/2 = 17 % aprox.
    But the probability of the underlying close above + 0.90 ,the atm call price, is higher , aprox. 34 % , looking at the delta. So the seller has a 66 % probability of winning.

    And also If the market maker sells the two sides, call and put, they have a 0.66 probability of winning. That is what says a normal distribution, right?
    Can anyone argue that the probability is 0.83 ? One time I almost thought this.

    _Is that a market makers consensus , to price atm options with a win probability of 0.66 ? , Why not 0.50 or 0.75, why not at 1,5 sd or 2 sd ?

    And talking about probabilities , this is probably a stupid question .

    Thanks.
     
  7. You could download 1 year of SPY quotes and check how many times SPY closed greater than +/- $1.80 on Wednesdays and Fridays - option expiry day.

    SPY Historical Dara
     
    elitenapper likes this.
  8. Robert Morse

    Robert Morse Sponsor

    No, it is pricing in a range of $1.80, not 3.60. And, I have no idea where you got that probability from.

    You are also making this way too complicated. If you think market participants are wrong and the actual move will be more, then you should buy it. You don’t have to buy the straddle. If you are bullish and believe the stock will go up more than $.90 just buy it and take your chances knowing that you have to exit either way at the end of the following day.

    That math is simple, down, up less than $0.90, held until near end of day, you lose. Up more than $0.90, you win. You need a process for a directional trade not calculate vol or Probability of the stock going up in any one day based on market prices.
     
    Last edited: May 9, 2018
  9. raf_bcn

    raf_bcn

    Thanks.
    I suspect you know that. Can you give me a clue.
     
    #10     May 9, 2018