[ericjang]

Good idea, but actually you'll probably want to look at the option markets as well, to take account the exact strike price at which Musk wishes to take Twitter private. If you only look at spot price (i.e. TWTR stock), then you need some way to factor out all the other beliefs market participants have about Twitter (e.g. stat-arb correlations with NASDAQ index).

As of time of writing, the delta on a $55 TWTR call option expiring 2 months from now is 0.297, representing a ~30% probability it will be in-the-money. But you still need to subtract the probability that the share price gets there without Mr. Musk's help.

You can also google "merger arbitrage" on google scholar to find some more maths on the subject.

[sword_smith]

Good point. The spot price is definitely not the most accurate measure of this probability. For liquid stocks with advanced derivates it's probably possible to find a better probability using one of those advanced derivatives.