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Spring 2011
Homework #3
(10 points)
(due Friday, February 11, by 3:00 p.m.)
No credit will be given without supporting work.
1.
During two-and-a-half years of research, bio-psychologist Onur Güntürkün
discovered that when people kiss, they turn their heads to the right roughly twice
as often as to the left.
(Güntürkün, O.
Human behaviour: Adult persistence of
head-turning asymmetry.
Nature
,
421,
711
, (2003).)
Suppose the probability that a person would turn his/her head to the right is
2
/
3
, and
the probability that a person would turn his/her head to the left is
1
/
3
.
A couple is
planning a kiss on Valentine’s day.
Assume that their choice of which way to turn
their heads is independent of each other.
a)
What is the probability that they would both turn their heads to the right (and kiss)?
b)
What is the probability that they would bump noses (i.e., choose the opposite direction
to turn their heads)?
Similar arguments with
3
/
4
and
1
/
4
predict phenotypic ratios of 9:3:3:1 in F
2
offspring in
Mendel's dihybrid crosses.
2.
From a group of 16 male and 9 female armadillos, Noah must choose two to
travel on his ark.
Unable to distinguish between male and female armadillos,
Noah must choose at random.
a)

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