I tried to rush the angry comment about how it all is wrong, but a few second ater posting the comment (oops) I understood. I’ve seen a great example since the school genetics: when two heterozygotes cross (Aa is crossed with Aa), frequency of homozygotes among the descendants with dominant trait is 1⁄3. AA Aa aA aa (may never survive to the adulthood. Or AA may not survive. Or both survive, but we aren’t interested)
There may be something that influences the 1:2:1 proportion (only in one side?), but it’s a “You flip a loaded coin. What’s your bet on it falling heads?” case.
Most of the probabilities are epsilon, and/or 100%-epsilon, and/or larger/smaller epsilons (for “unsure in known psychology” and “unsure in known logic” probability difference).
Maybe will do next year, because I have a lot to change.