Oteha Valley Primary School ban Bday Cakes tvnz
AUCKLAND.
at least 2 errors there. sorry.
A. "every day there is at least 1 birthday at the
school??" 400 pupils.
Oteha Valley Primary School ban Bday Cakes tvnz
AUCKLAND.??????????? Suppose 200 school days x 2
cakes, A and B, every day
bcc; nzm nzmm newss andr
dear editor,
B. or some cl***** have 4 birthdays/ week.?
teletext tvnz one news newstalk zb.
expectecd value (bdays on any day) m =3D 400 / 365 ~=3D
1.1
poisson distribution.
Pr (0) =3D e^ -m =3D exp(-1.1) ~=3D 0.33
some days no pupils will have a birthday, some days
will have 1 bday, and some more.
no. there is a 1/3 chance that there will be no
birthdays on a particular day. so NOT EVERY DAY at
least 1...........birthdays.
I challenge dispute that assertion.
so there could usually be 100+ days of a year with no
birthdays, probably.
it is an atom of chance that there are no birthdays
for 1460 days. 2920.
years 2oo5 06 2oo7. // 1896-1900-1904.
if e.g. every child is a leap baby.
would births be induced.
assignment problem? astronomical odds.
B. expect 1/2 birthday per class per week.
Poisson discrete probability function.
Prob (X =3D 4) =3D e ^-m x m^X / X!
=3D e^-.5 *.5^4 / 4!
=3D 1/ 633.
twins birthday problem.
primary school 400 pupils
ages 5-11 years. range =3D 7yrs?
siblings-- more likely to share a birthday.
because multiple births and 12 month?? gap between
children. ///seasons.
and siblings similar cl*****, IQ nature-nurture.
sometimes 4 birthday cakes in yr. year?
suppose 52 weeks/ yr and 26 children per class.
number of birthdays / class / week =3D 1/2 =3D 26/52 =3D
0.5.
Hadyn Jones tvnz, 4/4/08.
ONE News 630 pm.. Check Query.
hi, interesting maths...
Suppose 200 school days x 2 cakes exactly, A and B,
every day, and nil birthdays on non-school days/.
=3D 400 pupils.
a bit silly so try to stick to what hadyn actually
said, top of this msg.
(200A)(200B) =3D 400 ! / 2^200. Permutation Factorial A
or B. uncertain.
For the first time in 60 years I guessed:??
( 2n ) ! =3D ( n !)^2 / 2^n. ??
clearly wrong because ( 2n ) ! is greater and
contains prime factors e.g. 101 103 107 109...
Probability =3D (400 / e) ^400 / (2^200 x 365 ^400.)
=3D (1.1 / e)^400 / 2^200
=2E. =3D 400x (log 1.1 =96 log e) =96 200x log2
=3D 10 ^ -217 =3D 1/ (100^108) =3D 1/ googol ^2
ouchh!!xxxxxxxxxxxxxxxxxx
=3D .000 [216 zeroes] =851, APPROXIMATELY.
Extremely ^ to the extremely rare.
---------- my first envelope calculation.
take first 200 pupils and link them to 200 different
school days.
=3D 200 ! factorial ways.
=3D 200*199*198*197*............*2*1.
do the same with the second 200 pupils.
it is extremely xxxx !!!! unlikely!
compare 400 birthdays uniformly scattered on 365 days.
probability =3D ( 200 !)^2 / 365 ^ 400
=3D (200/ 365 e) ^400 =3D (200/ 1000) ^400
=3D 5^-400 =3D 125 ^-133 ~=3D 10 ^-300.
=3D .000 [300 zeroes..] ..1.
probability.
Yours truly, Donald S. McDonald WGTN
04/389-6820.
Researched with frank c 6.04.08 NZST.
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