Correlation, allocation in a portfolio. Calculation methods - page 8

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Aleksey Nikolayev:

The probability of there being a coincidence is very high (the birthday paradox)

Is there evidence for this in real samples or is it pure theory?

For example, on pupils in school classes should show up: every second class (even more often) should have pupils born on the same day. I went to school, then to technical school, then to university. There were about 30 of us in the school class, about 25 in the technical school group, 20 in the institute. I don't remember a situation with birthdays on the same day anywhere.

 
PapaYozh:

For example, it should show up on pupils in school classes: every other class (even more often) should have pupils born on the same day.

How is that?

Two classes are 40-50 people?

"Should be" only if there are 367 or more pupils in two classes....

 
Dmytryi Nazarchuk:

How's that?

Two classes is 40-50 people?

What's not to understand?

The paradox of birthdays. In a group of 23 or more people, the probability of at least two people having the same birthday (date and month) exceeds 50%.

A school class probably fits as "a group of 23 or more people.

That's what I'm saying, in every other school class there should be students born on the same day.

But this, from my observations, is not the case.

 
Dmytryi Nazarchuk:


"Should be" only if there are 367 or more pupils in two classes....

You should read about this "paradox".

ru.wikipedia.org/wiki/paradox_of_birthdays

 
PapaYozh:

What's not to understand?

The paradox of birthdays. In a group of 23 or more people, the probability of at least two people having the same birthday (date and month) exceeds 50%.

In a school class, it probably fits as "a group of 23 or more people.

That's what I'm saying, in every other school class there should be students born on the same day.

But that, in my observation, is not the case.

There should be students born on the same day in every other school class, with a 50% probability of being born on the same day. It's like flipping a coin.

Just "must meet" is for a group of at least 367

 
Don't get bogged down in heresy.
No one ever owes anyone because of any inference, no matter how logical it may be.
And randomness, while we are on the subject, exists if and only if absolutely all outcomes of events are equally probable.
The odds of being born on one
of any one day of the year are not equal. Hence the alleged paradox, which is probably not a paradox at all, as 9 women will not give birth in a month.
 
Renat Akhtyamov:

The probabilities of being born on any one day of the year are not equal.

Okay, give me a prouf.

 
Dmytryi Nazarchuk:

All right, give me a prouf.

Well, first of all, not every year has the same number of days as the year before. Second, Tuesday of this year is not Tuesday of the previous year. Thirdly, it's not exactly 9 months, but plus/minus. The saying 'cat of March', finally.
Well, then turn on your brain and figure out the coincidences that influenced the birthday on the same date.
When you are completely out of your mind, it is either a paradox or an accident ;)
 
Renat Akhtyamov:
Well firstly not every year has the same number of days as the previous year. Secondly, the Tuesday of this year is not the Tuesday of the previous year. Third, it's not exactly 9 months, but plus/minus. The saying 'cat of March', finally.
Well, then turn on your brain and figure out the coincidences that influenced your birthday on the same date.
When you are completely out of your mind, it is either a paradox or an accident ;)

bullshit.

If you take samples of the same size, obvious nonsense.

 
Dmytryi Nazarchuk:

nonsense.

If you take samples of the same size, obvious nonsense.

Take samples?
This is already nonsense.
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