A farmer (on an island of course) has 100 cows in a barn.

Each is brown or blue, and each was purchased from a supplier that randomly sells a brown or a blue cow with equal likelihood.

 

 

The farmer tells a farmhand to go in and let a brown cow out. A brown cow is let out.

 

What is the expected proportion of brown cows to total cows?

Edited June 22, 201213 yr by md65536

Sorry - changed my mind

Edited June 22, 201213 yr by Joatmon

Still 50% is the most likely expectation

Still 50% is the most likely expectation

Unless I worded it wrong, the expected proportion will be the mean of all equally probable possible proportions. The mean can be fractional. You've given the mode.

"What is the expected proportion of brown cows to total cows? "

Where?

Same answer as the one I posted in the other one?

Unless I worded it wrong, the expected proportion will be the mean of all equally probable possible proportions. The mean can be fractional. You've given the mode.

 

You can't expect the actual result to be.

 

(I'm just throwing out my $.02, even if it might be overpriced, and taking "expected proportion" somewhat literally, as "most expected proportion")

 

Does "expected proportion" have a defined meaning in statistics? (not my field) I don't assume it has one in brain teasers.

You can't expect the actual result to be.

 

(I'm just throwing out my $.02, even if it might be overpriced, and taking "expected proportion" somewhat literally, as "most expected proportion")

 

Does "expected proportion" have a defined meaning in statistics? (not my field) I don't assume it has one in brain teasers.

Not my field either, and I'm in over my head now.

I didn't mean for this to be a brain teaser or trick, just a quick stats puzzle.

 

As mentioned by someone in a similar thread, these puzzles assume a Bayesian interpretation of probability, where it's possible to reason about an uncertain count of brown cows. So the expected count expresses probability, and can be fractional until enough information is known to make the count certain, in which case it would be integral. I meant for the expected proportion to represent the uncertain proportion, given only what information is in the puzzle.

 

Sorry about the ambiguity!

 

Rather than being sorry about the ambiguity, try clearing it up.

Answer my earlier question.

When you say "What is the expected proportion of brown cows to total cows?" which cows are you referring to?

All cows on the island, those in the barn or those outside the barn?

 

Also, cows are not blue unless you paint them.

If the vendor supplies blue cows it's possible that the paint washes off in the rain. After a while all cows will be brown (or white or whatever).

 

Is it reasonable to assume that cows do not change colour?

 

"During your daily contact with your cattle, always be on the lookout for any physical or behavioral changes. Symptoms indicating illness include listlessness, pale coloring,

limping, loss of appetite, teeth grinding, coughing, and abnormal temperature"

from

http://www.farmsanctuary.org/wp-content/uploads/2012/06/Animal-Care-Cattle.pdf

Yeah if my answer isn't in any way correct, and the cows were painted blue, then the paint could have worn off before you asked the question, making it 100% brown cows, or it could be 0% because someone painted all the brown cows blue.

Rather than being sorry about the ambiguity, try clearing it up.

Answer my earlier question.

When you say "What is the expected proportion of brown cows to total cows?" which cows are you referring to?

 

The 100 cows specifically mentioned in the puzzle.

 

 

Where they are is irrelevant. The only point in mentioning the barn is to justify the reasoning that you don't have any further info about the cows because they're hidden. This isn't a trick question.

 

 

 

 

 

 

Yeah if my answer isn't in any way correct, and the cows were painted blue, then the paint could have worn off before you asked the question, making it 100% brown cows, or it could be 0% because someone painted all the brown cows blue.

This is just a stats puzzle, not a lateral-thinking puzzle. The puzzle implies the existence of blue cows. That can be assumed.

Is the answer you are looking for (1+ 99/2) /100 ?

Is the answer you are looking for (1+ 99/2) /100 ?

No. The other 99 cows are not equally likely to be brown or blue.