maths error in newspaper?

Raycyst

I wonder has this been brought up on the forum before?

Three generations of the same family born on the same day

http://www.express.co.uk/news/uk/817488/three-generations-family-born-on-same-day wrote:

Steve Winterbottom Snr, 63, and son Steve Winterbottom Jnr, 35, were both born on June 4.
In a remarkable set of events, they now share their birthday with the latest addition to the family - newborn Alexa Ray.



Bookies Ladbrokes have put the chances of Steve Winterbottom Snr, Steve Winterbottom Jnr and Alexa all being born on the same day are 48,000000/1.

Are the bookies correct?
Does the bookies story hold water?


I think perhaps not. The bookies made a booboo.


think about it before checking!.

Correct odds are 365 x 365.

It's only correct to say 44 million if the three generations must be born on a particular named day, rather than merely being born on the same day.

Healio

1/((365^-1)*(365^-1)*(365^-1) = 48627125

Raycyst

But why do you have three 365s?

The granddad can be born on any day.

4068ac1elhodqr

133,225/1, but summer births are slightly more popular anyway so reduce that factor slightly.

Sept is the most common month due to many folks finding time to get jiggy jiggy wit'it over the Christmas holidays, in these parts anyway.

Raycyst

Well, if the odds of being born on each day isn't 365 to 1 then that changes the problem significantly, and makes it much harder.

Can it even be solved in that case?

Say for example the odds of being born on a even numbered day are ten times the odds of being born on a odd numbered day, how does that change the calcs?

The situation would be that you'd be have about 91% chance of being born on an even day and about a 9% chance of an odd day. Then, you'd have odds of about 183 to 1 of landing on a particular day within the odd or even groups.

Hmmm. That's tricky.

What'd be the odds of three generations all being born on the same day under that system?

Yourself isit

Raycyst wrote: »

But why do you have three 365s?

The granddad can be born on any day.

Oh yeah. Good point.

Healio

Raycyst wrote: »

But why do you have three 365s?

The granddad can be born on any day.

Bad use of language in the article. They probably got both answers off the bookies but one of them is less impressive :pac:

Raycyst

Yep, let's blame the article. :cool: :pac:


When is the answer of approx 48 million correct?

There are very few circumstances when it is, in the real world.

If a women was pregnant, and she was infallible at maths, and you asked her;

What are the chances of your child being born on the 10th July say, and then that child having a child also on the 10th July, and then that new child also having a child on the 10th July? In other words, three generations all being born on a particular named day.

Would the woman give an answer of approx 48 million?

I say no; the women would answer as follows.
(think before checking, this is quite logical)

I'm already pregnant. I know my due date. It is nowhere near the 10th July. Therefore the odds of me having a child on the 10th July are very small. The odds of future children being born on that day is approx 365 to 1.

The problem is the woman is pregnant when you ask her and she likely knows her due date, which changes the odds of her having a baby on a particular named day.

You'd have to ask her the question before she fell pregnant.

That's what I mean when I say there are very few circumstances in the real world where 48 million is the correct answer to the question.

That's what I mean when I say there are very few circumstances in the real world where 48 million is the correct answer to the question.




There is another easy way to expose the bookies mistake.
If you asked, what are the odds of a son being born on the same day as its father?
Is it 365 to 1?,
or is it 365 X 365 to 1?

Why would it be 365 x 365 to 1? :eek:

That's the mistake they made with the three generations, and no-one noticed.

:rolleyes:

Healio

Raycyst wrote: »

Yep, let's blame the article. :cool: :pac:


When is the answer of approx 48 million correct?

If I asked you as a single man with no kids what price is my son, grandson and great-grandson son to be born on the same day.

Raycyst

When is the answer of approx 48 million correct?

Healio wrote: »

If I asked you as a single man with no kids what price is my son, grandson and great-grandson son to be born on the same day.

But the odds of that aren't 48 million to 1.

the son can be born on any day.
365 to 1 that the grandson is also born on the same day.
also 365 to 1 that the great-grandson is also born on the same day.

Therefore, it is 365 x 365 to 1 (133,225 to 1) that all three are born on the same day.

M.T. Cranium

The odds might be as low as 1 in 3,650 if let's say the first occurrence was random but the second one was the result of a conversation along the lines of "wouldn't it be great if we had a kid born on the same day as me and my dad?" and they timed it but still no guarantee of a birth coming on the right day, just perhaps within two weeks so about a one in ten chance given that dates in the middle of the period might be more likely than on the edges of the period.

And if that same conversation had happened in both instances, the odds then fall to about one in a hundred (if they were fertile folk).

Peter Flynt

133,225 to 1