Matematické Fórum

zuz · 07. 12. 2009 21:48

Ahoj, zapasim tady s par ukolama na statistiku a vubec nevim, co s nima. Uz jsem hledala na internetu, ale nenasla jsem nic, co by mi to nejak pomohlo vysvetlit, tak se obracim na Vas :)

Prvni zadani je: hrac si vybere 6 cisel v rozmezi od 1 do 40. jaka je probabilita toho, ze presne tehle 6 cisel se vylosuje? dale, jaka je probabilita, ze presne 4 z tech sesti cisel budou vylosovana? a jaka je probabilita, ze nejmene 4 z tech 6 budou vylosovane.

Druhe je: Na jednu stranku v knize pripada prumerne 1.3 chyby v textu.
a) mam udelat discrete probability distribution.. nevim, jak se tomu rika cesky?.. tech chyb na dve stranky textu
b) co je prumerne cislo chyb, ktere se nachazi na kazdych dvou strankach knihy
c) jaka je variance a standard deviation tech chyb na dvou strankach textu
d) kdyz nekdo, kdo to kontroluje, precetl ctyri stranky textu a nenasel ani jednu chybu, tak co z toho muzu predpokladat?

pokud byste me nekdo mohl popostrcit treba na jenom jedny veci z tehle, tak vam budu moc vdecna, dekuji :)

Kondr · 07. 12. 2009 23:57 — Editoval Kondr (08. 12. 2009 00:01)

Should be: "What is the probability", not "jaka je probabilita".
1) I suppose he chooses 6 *different* numbers and that after being picked, the numbers are not returned.
There are ${40\choose 6}$ different 6-tuples of numbers from 1 to 40, probability of guessing the right one is thus $\frac{1}{{40\choose 6}}$

2) This task involves Poisson distribution.
a) For two pages, just plug $\lambda=2.6$ and make a table like this
x 0 1 2 3 ....
p(x) f(0,2.6) f(1,2.6) f(2,2.6) ....

The numbers in bottom line should be evaluated by calculator.

b) 2.6

c) see the formula for variance of Poisson distribution. Standard deviation is square root of variance.
d) this seems to be a tricky one. Certainly we cannot say anything about other pages. We just could guess that he failed to spot a mistake, since probability of no mistake being on 4 sites is really low.

************
If the subject is taught in English, I don't think there's a reason to mess with those Czech terms.

zuz · 08. 12. 2009 12:21

thank you so much!!! you helped me a lot!! :) i really appreciate it.

Matematické Fórum

#1 07. 12. 2009 21:48

Statistika - Probabilita

#2 07. 12. 2009 23:57 — Editoval Kondr (08. 12. 2009 00:01)

Re: Statistika - Probabilita

#3 08. 12. 2009 12:21

Re: Statistika - Probabilita

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