Well. as an intro to this blog let us say tha I sell options. I don't buy them.A stock can only  go up, down, or remain about the same. The probabilities are about equal. that is 1/3 in each direction. Then it will either reach the options strike or it won't.
That is the buyer has 1/3*.5 = .17 of being successful
The seller has 1.0 - .17 = .83 chance of being successful.
If the underlying is trending that alters the picture.  Suppose the trend is up & the last year's evidence was .90 up
and .10 down. Now we have   ,9 * .5= .45 of reaching the call strike and only .1 * .5 = .05 of reaching the put strike.

That's enough food for thought for new.
Any interested  members are welcome to to post tid-bits, ask questions or contribute. I'm logging off and going for a drink.