What are my chances?

[learner]

Have a brain teaser for you all....

One fine day, I walk into a fish shop. Being a total newb at sexing cories, I randomly scooped out 6 cories and went home happy.

Now, for the million dollar question.....

What are the chances that I will at least be able to get a pair of cories for breeding from my 6 cories?

[benny]

Anybody took probability for maths?

So it's 50% X 50% X 50% X 50% X 50% X 50% that it's all males and also the same for females?

Big money involved here.

Cheers,

[ranmasatome]

i dont know about corys but i know that for certain fishes they only bring in the males cos the females dont sell well.. so to start off...you already had 100% chance of getting all males..lol..but that in itself is also a probability...geez..

[crandf]

You have 31/32 chance
Basically mmmmmm and ffffff are what you dun want, so the combinations in between are where your pairs are, so use binary.

[benny]

So there's a 96.8% chance that you have at least a pair in the group of 6 then?

Cheers,

[gks]

Althoughthe following site is talking about angelfish breeding, but the idea is similar for breeding egg-layers that are difficult to determine the gender:

http://www.angelsplus.com/breeding.htm#acquire

Basically, the more you put inside, the better the probability of getting at least two different genders. However, whether they pair up and breed depends on many other factors. Essentially, you need to provide a conducive environment for them to make love.

[stormhawk]

In a group of 6 corys, consider yourself lucky if you have a good ratio of the sexes. Sometimes buying 6 does not necessarily mean you'll get both sexes.

I have found batches where there are at least 90% males in a bag or in a tank.
Unless you bought 6 of the dwarfs, then my guess is you probably might have a skewed sex ratio among the corys you bought. Good luck.

[andrewtyr]

ok, since we are in the topic, so let me guess - Cory spawns normally consist of higher male ratio?

[juggler]

So there's a 96.8% chance that you have at least a pair in the group of 6 then?

Cheers,

Here's what I learnt in school:

Chance of getting at least a pair = 1 - (Chance of getting all males + chance of getting all females)

Assuming equal sex ratio in the tank, then:

Chance of getting a pair in 6 fish = 1 - (0.5^6 + 0.5^6) = 0.96875

Same answer.

[Justikanz]

ok, since we are in the topic, so let me guess - Cory spawns normally consist of higher male ratio?

Think I read somewhere it also depends on temperature of the water and the pH... Too much to one end will result in too many males and the other females...

[benny]

hmm... I thought it's either you get a pair, or you don't. So 50%? No? Didn't realise the probability is so high!!

Cheers,

[andrewtyr]

hmm... I thought it's either you get a pair, or you don't. So 50%? No? Didn't realise the probability is so high!!

Cheers,

You really made it sound like Mark Lee's gambling theory - 50-50, either you win or you don't!

[benny]

You really made it sound like Mark Lee's gambling theory - 50-50, either you win or you don't!

I got F9 for maths, but score highest for probability last time. Also don't know what happened.

CHeers,

[stormhawk]

ok, since we are in the topic, so let me guess - Cory spawns normally consist of higher male ratio?

Not necessarily. There are many factors that affect the eventual sex ratio of the fry, including pH, temperature, etc. These also play a role in the development of fry for other fish species and not just corys alone.

What I'm really trying to say is on occasions you don't get enough of both sexes when you buy them from the shops. So don't be too sad if you bought 6 and found out all of them were of one gender. Besides, if there was only 1 female, then that's all you need, provided the other 5 males were fertile.