Hi all,

I formed a stock universe where the program seeks cointegrated pairs using python (stocks from SP500). Also there are functions to plot the spread.
So I defined z-score, linear regression and price ratio functions.
Here are GILD/WFC pair, for instance. The slope for our combination is 0.74
1. What exactly positions should I open using the z-score plot at the current moment (when z-score below 0 , around -2)? Should it be opened short WFC vs long 0.74*GILD or long WFC vs short 0.74*GILD ?
2. about fitting the spread to OU process. Here are the formula to compute the speed of mean-reversion .
B - slope = 0.74
So in our example : the speed = -lnB/t = -ln0.74/1/252 = 0.3/0.00396 = 75.75 days for reverting to the equilibrium level , are these arguments correct ?

2
def hedge_ratio(Y, X, add_const=True):

For simplicity, the notional weights for  y_target_shares = ±1  and  X_target_shares = ∓hedge  are for purpose of the lecture, and may not be applicable to the specifics of your actual pairs.