Quote Originally Posted by paulh View Post
The formula is p to the nth power (pn) < 0.01.
p = probability of not getting what you want from a single egg
n = number of eggs

Here's the easy way to calculate the formula. Using the calculator in Windows' Accessories folder, choose view --> scientific. Then enter the value of p, press the xy key, enter a value for n, and hit the <ENTER> key.

Example 1: You have a normal looking ball python that could be heterozygous albino. You mate it to an albino ball python. You want albinos, and you do not want normal looking babies. The probability of getting an albino is 0.5, and the probability of getting a normal looking baby (p) is 0.5.

Multiply 0.5 by 0.5 for as many times as it takes to get a number less than 0.01.
In this case, 0.5 * 0.5 * 0.5 * 0.5 * 0.5 * 0.5 * 0.5 (or 0.5 to the seventh power) = 0.008 (rounded). In other words, seven normal looking snakes and no albino snakes has less than a 0.01 probability of occurring by chance.

Example 2: You have a normal looking ball python that could be heterozygous albino. You mate it to a normal looking, het albino ball python. You want albinos, and you do not want normal looking babies. The probability of getting an albino is 0.25, and the probability of getting a normal looking baby (p) is 0.75.

Multiply 0.75 by 0.75 for as many times as it takes to get a number less than 0.01. In this case, 0.75 to the seventeenth power = 0.008 (rounded). In other words, seventeen normal looking snakes and no albino snakes has less than a 0.01 probability of occurring by chance.

The above assumes that albinos and nonalbinos have an equal chance of hatching. This is not always true. Or you may have plain bad luck. But it is the place to start, and almost all of the time it will give the right answer.
Nice to see another match nerd, but I just want to point out, this equation is only getting you to 99% certainty. While that's pretty good. Nature just doesn't always follow math. IMHO, HetxHet is three clutches of at least 6 viable eggs(only one more egg than purported above by maths). HetxHom is one clutch of at least 6 viable eggs where the snake in question is known absolutely to be a parent. In the case of males, it must be obvious that there was no retained sperm preventing the male in question from seeing the female. In the case of a female, if she's a virgin, first clutch should be good, if she's not, again, it needs to be obvious that she did not retain sperm from the previous year, regardless of who bred her.

This brings up another question in my mind. I've seen several times lately of people underselling their snakes. Not enough blushing on a possible firefly, call it a pastel and sell yourself short. Hopefully the person getting it is happy with that. I know I would be. But what do you do in this case. Refund, take the snake back and re-sell for more? I'm perfectly happy with the sale being final if I undersell myself, but it could be an interesting conundrum, especailly if someone is working on something like a vanilla cream or vanilla scream project. Or You have BELs with extra genes.