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    • Prof_Green
    • By Prof_Green 13th Mar 18, 8:55 PM
    • 117Posts
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    Prof_Green
    Pups puzzle.
    • #1
    • 13th Mar 18, 8:55 PM
    Pups puzzle. 13th Mar 18 at 8:55 PM
    A dog breeder says she has two new baby Labradors to show you, but she doesn't know whether they're male, female, or a pair. You tell her that you want only a male, and she telephones the fellow who's giving them a bath. "Is at least one a male?" she asks him. "Yes!" she informs you with a smile. What is the probability that the other one is a male?
Page 1
    • maninthestreet
    • By maninthestreet 13th Mar 18, 9:53 PM
    • 15,275 Posts
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    maninthestreet
    • #2
    • 13th Mar 18, 9:53 PM
    • #2
    • 13th Mar 18, 9:53 PM
    1 in 4 - I think.
    "You were only supposed to blow the bl**dy doors off!!"
    • z1a
    • By z1a 13th Mar 18, 9:54 PM
    • 1,259 Posts
    • 1,196 Thanks
    z1a
    • #3
    • 13th Mar 18, 9:54 PM
    • #3
    • 13th Mar 18, 9:54 PM
    50:50 .
    • Prof_Green
    • By Prof_Green 13th Mar 18, 11:18 PM
    • 117 Posts
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    Prof_Green
    • #4
    • 13th Mar 18, 11:18 PM
    • #4
    • 13th Mar 18, 11:18 PM
    Both wrong!!
    • maninthestreet
    • By maninthestreet 13th Mar 18, 11:30 PM
    • 15,275 Posts
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    maninthestreet
    • #5
    • 13th Mar 18, 11:30 PM
    • #5
    • 13th Mar 18, 11:30 PM
    Thinking about it again, the possible combinations are male/male, male/female and female/female. So the odds are 1 in 3.
    "You were only supposed to blow the bl**dy doors off!!"
    • Prof_Green
    • By Prof_Green 14th Mar 18, 12:12 AM
    • 117 Posts
    • 70 Thanks
    Prof_Green
    • #6
    • 14th Mar 18, 12:12 AM
    • #6
    • 14th Mar 18, 12:12 AM
    Thinking about it again, the possible combinations are male/male, male/female and female/female. So the odds are 1 in 3.
    Originally posted by maninthestreet
    Female/female is not a possibility as at least on is male.

    The answer is 1 in 3 though.


    Possible combinations are male/male, male/female and female/male

    So there are 3 possibilities with at least one male, but in only 1 of them is the other pup a male.
    • miriamac
    • By miriamac 14th Mar 18, 1:56 AM
    • 292 Posts
    • 718 Thanks
    miriamac
    • #7
    • 14th Mar 18, 1:56 AM
    • #7
    • 14th Mar 18, 1:56 AM
    Female/female is not a possibility as at least on is male.

    The answer is 1 in 3 though.


    Possible combinations are male/male, male/female and female/male

    So there are 3 possibilities with at least one male, but in only 1 of them is the other pup a male.
    Originally posted by Prof_Green
    Male/female and female/male are exactly the same dogs.

    Displayed differently.
    • Prof_Green
    • By Prof_Green 14th Mar 18, 2:18 AM
    • 117 Posts
    • 70 Thanks
    Prof_Green
    • #8
    • 14th Mar 18, 2:18 AM
    • #8
    • 14th Mar 18, 2:18 AM
    Male/female and female/male are exactly the same dogs.

    Displayed differently.
    Originally posted by miriamac

    No they are not, not if you think of them a pup A and pub B

    or as the first and last born

    if there were born the first could be male and second female or
    the first female and the second male so they are not the same
    and you will get two male/female pairs for every male/male pair.
    • Pyxis
    • By Pyxis 14th Mar 18, 7:16 AM
    • 34,938 Posts
    • 129,737 Thanks
    Pyxis
    • #9
    • 14th Mar 18, 7:16 AM
    • #9
    • 14th Mar 18, 7:16 AM
    Unfortunately, the problem here is not with the mathematics, but with the semantics of the question.

    If an absolute answer is required, rather than just a debate on semantics, then the question has to be worded in a better way, I'm afraid, otherwise two answers are possible, and you'll be debating it until the cows come home and beyond.

    For the reason why, you'd have to read right through this long table-tennis match of a discussion on this other forum's thread from 2006.

    Have fun, chickadees!
    (I just lurve spiders! )
    INFJ(Turbulent).

    Her Greenliness Baroness Pyxis of the Alphabetty, Pinnacle of Peadom
    Founder Member: WIMPS ANONYMOUS
    • indesisiv
    • By indesisiv 14th Mar 18, 8:02 AM
    • 5,663 Posts
    • 18,657 Thanks
    indesisiv
    Female/female is not a possibility as at least on is male.

    The answer is 1 in 3 though.


    Possible combinations are male/male, male/female and female/male

    So there are 3 possibilities with at least one male, but in only 1 of them is the other pup a male.
    Originally posted by Prof_Green
    But there is no valid relationship between the 2 dogs.

    You could have 10 dogs, of which 9 are male, what's the probability of the other being male ... 50:50

    Just because one dog is a male has no statistical bearing on the other dog at all.

    It similar to a coin toss. If you flip a head then a head, what is the chance of the next one being a head? (50% chance) It is only when you start to calculate the cumulative possibility of them all in a row that it stops being 50:50
    “Time is intended to be spent, not saved” - Alfred Wainwright
    • Prof_Green
    • By Prof_Green 15th Mar 18, 12:41 AM
    • 117 Posts
    • 70 Thanks
    Prof_Green
    Unfortunately, the problem here is not with the mathematics, but with the semantics of the question.

    If an absolute answer is required, rather than just a debate on semantics, then the question has to be worded in a better way, I'm afraid, otherwise two answers are possible, and you'll be debating it until the cows come home and beyond.

    For the reason why, you'd have to read right through this long table-tennis match of a discussion on this other forum's thread from 2006.

    Have fun, chickadees!
    Originally posted by Pyxis

    My be easier if we think of coins and head or tails.

    I have spun two coins, at least one is heads, what are the chances both are heads?

    Well normally 1 in 4 as the possibility are HH HT TH and TT
    however we can rule out TT as one is heads which leaves us
    with HH HT & TH

    We can see that if one is known to he H then only one of the 3 possibilities
    has the other one heads.
    • z1a
    • By z1a 15th Mar 18, 1:57 PM
    • 1,259 Posts
    • 1,196 Thanks
    z1a
    Both wrong!!
    Originally posted by Prof_Green
    No. The answer IS 50:50.

    The chances of any dog being a male is evens, regardless of of any dogs before or after.
    • NBLondon
    • By NBLondon 15th Mar 18, 2:50 PM
    • 1,771 Posts
    • 9,453 Thanks
    NBLondon
    No. The answer IS 50:50.

    The chances of any dog being a male is evens, regardless of of any dogs before or after.
    Originally posted by z1a
    No the Prof is right...

    50% is the assumed probability of any given dog being male independent of any other conditions. What was asked for was the probability of Dog B being male - given that we already know one or both dogs is male.

    In real terms - it's a contrived question because a) the breeder should already know the sexes of the puppies and b) the bather would look at both puppies and answer "both male/both female/one of each"
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    • fairy lights
    • By fairy lights 15th Mar 18, 3:26 PM
    • 8,574 Posts
    • 28,529 Thanks
    fairy lights
    It's not really relevant anyway because I wouldn't buy a dog from a breeder who couldn't even tell what sex they were. Are they even Labradors anyway or are they large gerbils? Riddle me that.
    • Jackmydad
    • By Jackmydad 15th Mar 18, 3:33 PM
    • 2,491 Posts
    • 7,436 Thanks
    Jackmydad
    It's 50:50
    The 3:1 thing is mixing up the possible combinations with the possible sex of individuals.
    So if one dog is male, the other can still only be male or female.
    The fact that you can make three combinations of m / f is spurious.
    "Luck happens where hard work meets opportunity"
    • Jackmydad
    • By Jackmydad 15th Mar 18, 3:36 PM
    • 2,491 Posts
    • 7,436 Thanks
    Jackmydad
    It's not really relevant anyway because I wouldn't buy a dog from a breeder who couldn't even tell what sex they were. Are they even Labradors anyway or are they large gerbils? Riddle me that.
    Originally posted by fairy lights
    When I first read the question I thought that I wouldn't be buying a pedigree dog from anywhere.
    Far, far too many genetic problems with them.
    Give me a cross breed every time.
    "Luck happens where hard work meets opportunity"
    • z1a
    • By z1a 15th Mar 18, 4:07 PM
    • 1,259 Posts
    • 1,196 Thanks
    z1a
    No the Prof is right...

    50% is the assumed probability of any given dog being male independent of any other conditions. What was asked for was the probability of Dog B being male - given that we already know one or both dogs is male.

    In real terms - it's a contrived question because a) the breeder should already know the sexes of the puppies and b) the bather would look at both puppies and answer "both male/both female/one of each"
    Originally posted by NBLondon
    No, you and OP are wrong.
    • fairy lights
    • By fairy lights 15th Mar 18, 4:14 PM
    • 8,574 Posts
    • 28,529 Thanks
    fairy lights
    Far, far too many genetic problems with them.
    Give me a cross breed every time.
    Originally posted by Jackmydad
    So there's a 30% chance the puppy is male, 30% chance it is female and a 30% chance it's a mutant with hermaphroditic sexual organs.
    The other 10% is still on it being a large gerbil.
    • Pyxis
    • By Pyxis 15th Mar 18, 4:20 PM
    • 34,938 Posts
    • 129,737 Thanks
    Pyxis
    It's not really relevant anyway because I wouldn't buy a dog from a breeder who couldn't even tell what sex they were. Are they even Labradors anyway or are they large gerbils? Riddle me that.
    Originally posted by fairy lights
    When I first read the question I thought that I wouldn't be buying a pedigree dog from anywhere.
    Far, far too many genetic problems with them.
    Give me a cross breed every time.
    Originally posted by Jackmydad
    So there's a 30% chance the puppy is male, 30% chance it is female and a 30% chance it's a mutant with hermaphroditic sexual organs.
    The other 10% is still on it being a large gerbil.
    Originally posted by fairy lights
    Now this is turning into a thread I would enjoy!

    Stuff the maths and semantics...... let's talk mutant crossbreed gerbil!
    (I just lurve spiders! )
    INFJ(Turbulent).

    Her Greenliness Baroness Pyxis of the Alphabetty, Pinnacle of Peadom
    Founder Member: WIMPS ANONYMOUS
    • Jackmydad
    • By Jackmydad 15th Mar 18, 4:24 PM
    • 2,491 Posts
    • 7,436 Thanks
    Jackmydad
    So there's a 30% chance the puppy is male, 30% chance it is female and a 30% chance it's a mutant with hermaphroditic sexual organs.
    The other 10% is still on it being a large gerbil.
    Originally posted by fairy lights
    You missed out the 20% chance that it was a whole new sex never seen before.
    Zmale?
    I'm 120% sure of that incidentally!
    "Luck happens where hard work meets opportunity"
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