128 reputation
6
bio website victorandree.se
location Sweden
age 24
visits member for 2 years, 9 months
seen Jun 8 at 12:05

Swedish freelance web developer, economics student and PR rookie. Big believer in the semantic web and emerging web technologies. Experience with mainly Python, PHP, Javascript and Objective C.


May
21
awarded  Popular Question
Sep
1
awarded  Autobiographer
Jan
15
accepted Relationship between two random, normally distributed variables
Jan
15
comment Relationship between two random, normally distributed variables
I'm not discounting the possibility that my book is wrong; it has an awful lot of errors... If you stand by your latest answer?
Jan
15
comment Relationship between two random, normally distributed variables
Well, I'm starting to feel stupid here. We've been taught to consider $$D = aX + bY$$ which in this case should be $$D = -X + 0.7Y$$, but then I still get $$2ab\rho\sigma\sigma = 2 \cdot 0.7 \cdot -1 \cdot 0.8 \cdot 6 \cdot 7$$ which is negative?
Jan
15
comment Relationship between two random, normally distributed variables
Hm. The formula I have is $$D = aX + bY$$ and I used a = -1, b = 0.7. Then (from my book), $$\sigma^2_D = a^2\sigma^2_X + b^2\sigma^2_Y + 2ab\rho\sigma_X\sigma_Y$$
Jan
15
comment Relationship between two random, normally distributed variables
I see... but I don't see why. The formula I have to find the variance of D does not use squares. It's just $$a^2\sigma^2 + b^2\sigma^2 + 2abCorr(X, Y)\sigma\sigma$$ (I'm being sloppy with the subscripts here, but yeah).
Jan
15
asked Relationship between two random, normally distributed variables
Nov
6
comment Creating pairs of homo-, bi- and heterosexual boys and girls
I initially misinterpreted "if there are d bisexuals" to mean "exactly d". Thanks for the answer, it works smashingly!
Nov
5
awarded  Scholar
Nov
5
accepted Creating pairs of homo-, bi- and heterosexual boys and girls
Nov
4
awarded  Supporter
Nov
4
awarded  Editor
Nov
4
revised Creating pairs of homo-, bi- and heterosexual boys and girls
added 4 characters in body
Nov
4
awarded  Student
Nov
4
comment Creating pairs of homo-, bi- and heterosexual boys and girls
@Phira: The man should, however, also like to marry her (i.e. he should not be homosexual).
Nov
4
comment Creating pairs of homo-, bi- and heterosexual boys and girls
@Phira: Indeed she would be! I'm kind of unfamiliar with this whole area of mathematics, but I'll have a look at the Wiki page :)
Nov
4
asked Creating pairs of homo-, bi- and heterosexual boys and girls