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Quant版 - two interview questions
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相关话题的讨论汇总
话题: sigmax话题: sigmay话题: payment话题: sample话题: two
进入Quant版参与讨论
1 (共1页)
b******e
发帖数: 118
1
1. option1: $240 fixed payment
option2: 25% chance to win $1000
which one do you choose? What if the prob is 40%?
General question: 3 variables, value of fixed payment, probability and
corresponding payment(i.e. 3 numbers mentioned above), generate an algorithm
to make the decision to choose either one.
2. Two independent random variables, x--N(0,sigmax^2), y--N(0,sigmay^2),
where sigmax and sigmay are known, you have one sample from x and one sample
from y, but you don't know the exact
P****d
发帖数: 113
2
1. depending on your utility function.
for example, if your u(x)=x^p (0 then just compare E[U(X)]=prob*(corresponding payment)^p
and fixed payment.
2.MLE: joint likelihood function
L_{sigmax,sigmay }(X,Y) is proportional to
exp{-0.5*(X/sigmax)^2-0.5*(Y/sigmay)^2},
s.t. X+Y=Z.
the result is X=Z* sigmax^2/(sigmax^2+sigmay^2).

algorithm
sample
the

【在 b******e 的大作中提到】
: 1. option1: $240 fixed payment
: option2: 25% chance to win $1000
: which one do you choose? What if the prob is 40%?
: General question: 3 variables, value of fixed payment, probability and
: corresponding payment(i.e. 3 numbers mentioned above), generate an algorithm
: to make the decision to choose either one.
: 2. Two independent random variables, x--N(0,sigmax^2), y--N(0,sigmay^2),
: where sigmax and sigmay are known, you have one sample from x and one sample
: from y, but you don't know the exact

b******e
发帖数: 118
3
How do you get the result Z* sigmax^2/(sigmax^2+sigmay^2)? Could you please
explain it in detail?
Btw, for the utility function you mentioned in question 1, is there a
general way to determine its form, i.e. quadratic, exponential or whatever?
Thanks a lot!

【在 P****d 的大作中提到】
: 1. depending on your utility function.
: for example, if your u(x)=x^p (0: then just compare E[U(X)]=prob*(corresponding payment)^p
: and fixed payment.
: 2.MLE: joint likelihood function
: L_{sigmax,sigmay }(X,Y) is proportional to
: exp{-0.5*(X/sigmax)^2-0.5*(Y/sigmay)^2},
: s.t. X+Y=Z.
: the result is X=Z* sigmax^2/(sigmax^2+sigmay^2).
:

S*******D
发帖数: 47
4
For the second question, you can follow the orthogonal principle like this:
assume xhat = h*z
then e = x - xhat = x - h*z
By O.P.
E[e*z]=0
then
sigmax^2 = h*(sigmax^2+sigmay^2).
then
h = sigmax^2/(sigmax^2+sigmay^2).
Does it make sense?

algorithm
sample
the

【在 b******e 的大作中提到】
: 1. option1: $240 fixed payment
: option2: 25% chance to win $1000
: which one do you choose? What if the prob is 40%?
: General question: 3 variables, value of fixed payment, probability and
: corresponding payment(i.e. 3 numbers mentioned above), generate an algorithm
: to make the decision to choose either one.
: 2. Two independent random variables, x--N(0,sigmax^2), y--N(0,sigmay^2),
: where sigmax and sigmay are known, you have one sample from x and one sample
: from y, but you don't know the exact

1 (共1页)
进入Quant版参与讨论
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太冷清了 来个题吧Can garch model be a white noise?
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问两道probability的题求推荐C++和programming/算法面试书籍
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one statistic interview question[合集] 有没有free的quadratic optimization package?
相关话题的讨论汇总
话题: sigmax话题: sigmay话题: payment话题: sample话题: two