Heckman Selection

[Averagealex5]

I've ran a Heckman selection model for my data but i'm unsure how to interpret whether there has been any sample selection bias, can someone guide me on which portion of my data to look at?

I'm using the Maximum Likelihood method and get SIGMA and RHO as noted below. I think this of use but I'm unsure
Variable Coefficient STD. Error t-Stat Prob.
SIGMA 0.876222 0.059927 14.62150 0.0000
RHO -0.587447 0.145845 -4.027890 0.0001

Many Thanks,
Alex