In: Math
1.
Suppose that
Superman is the favorite hero of
3
5%
of
all DC Comics fans, Batman is the
favorite of 26% of fans, Wonder Woman is the favorite of 19%, Green Lantern is the favorite
of 12%, and the
Flash is the favorite of all the rest of fans
.
a)
If a
DC Comics fan
is selected at random, what is the
probability that
:
i.
T
he Flash is that person’s favorite superhero
?
ii.
T
he person’s favorite superhero is Batman or Wonder Woman?
iii.
T
he person’s
favorite superhero is not Superman
?
b)
If you were to randomly select
five
DC Comics fans
, what is the probability that:
i.
Batman
is the favorite superhero of all five people
?
2
ii.
No
ne of the
five
people
identify Green Lantern as their favorite superhero
?
iii.
All five people identify
Green Lantern
as their favorite superhero
or
all five identify
Wonder Woman
as their favorite
?
iv.
N
ot
all
five
people identify
the Flash
as their favorite superhero
?
v.
Superman is the favorite superhero of
at least
one of the
five
people
?
It is given that Superman is the favorite hero of 35% of all DC Comics fans, Batman is the favorite of 26% of fans, Wonder Woman is the favorite of 19%, Green Lantern is the favorite of 12%, and the Flash is the favorite of all the rest of fans i.e. 100%-35%-26%-19%-12% = 8% of the fans.
If a DC Comics fan is selected at random, the probability that the Flash is that person’s favorite superhero = 8% = 0.08
If a DC Comics fan is selected at random, the probability that the person’s favorite superhero is Batman or Wonder Woman
= Probability that the person’s favorite superhero is Batman + Probability that the person’s favorite superhero is Wonder Woman
= 26% + 19% = 0.26 + 0.19 = 0.45
If a DC Comics fan is selected at random, the probability that the person’s favorite superhero is not Superman
= 1 - Probability that the person’s favorite superhero is Superman
= 1 - 35% = 1 - 0.35 = 0.65
.
Assumption:
All the 5 DC Comics fans were selected independently.
If 5 DC Comics fans were randomly selected, the probability that Batman is the favorite superhero of all the 5 people
= (Probability that Batman is the favorite superhero of 1 randomly selected DC fan)5
= (26%)5 = (0.26)5 = 0.0011881376
If 5 DC Comics fans were randomly selected, the probability that none of the 5 people identify Green Lantern as their favorite superhero
= (Probability that 1 randomly selected DC Comics fan do not identify Green Lantern as the person's favorite superhero)5
= (1 - Probability that 1 randomly selected DC Comics fan identify Green Lantern as the person's favorite superhero)5
= (1 - 12%)5 = (1 - 0.12)5 = (0.88)5 = 0.5277319168
If 5 DC Comics fans were randomly selected, the probability that all of the 5 people identify Green Lantern as their favorite superhero or all the 5 people identify Wonder Woman as their favorite superhero
= (Probability that 1 randomly selected DC Comics fan identify Green Lantern as the person's favorite superhero)5 + (Probability that 1 randomly selected DC Comics fan identify Wonder Woman as the person's favorite superhero)5
= (12%)5 + (19%)5 = (0.12)5 + (0.19)5 = 0.0002724931
If 5 DC Comics fans were randomly selected, the probability that not all of the 5 people identify the Flash as their favorite superhero
= Probability that at least 1 of the 5 randomly selected DC Comics fans do not identify the Flash as the person's favorite superhero
= 1 - Probability that all of the 5 DC Comics fans identify the Flash as their favorite superhero
= 1 - (Probability that 1 randomly selected DC Comics fan identify the Flash as the person's favorite superhero)5
= 1 - (8%)5 = 1 - (0.08)5 = 1 - 0.0000032768 = 0.9999967232
If 5 DC Comics fans were randomly selected, the probability that Superman is the favorite superhero of at least 1 of the 5 people
= 1 - Probability that Superman is the favorite superhero of none of the 5 randomly selected DC Comics fans
= 1 - (Probability that Superman is not the favorite superhero of 1 randomly selected DC Comics fan)5
= 1 - (1 - 35%)5 = 1 - (1 - 0.35)5 = 1 - (0.65)5 = 1 - 0.1160290625 = 0.8839709375