Let X = the number of dropped calls experienced per day by
customers of a particular cell phone provider. This random
variable is
10
1.
2.
3.
4.
5.
Measurable
Discrete
Continuous
A failure
Indeterminate
0%
1
0%
0%
2
3
0%
0%
4
5
Let Y = the number of dropped calls experienced per day by
customers of a particular cell phone provider. Y has the
following probability distribution:
Y
0
1
2
3
Prob
.55
.30
.10
.05
What is the expected number of dropped calls per day?
10
1.
2.
3.
4.
5.
0
0.5
0.65
2.0
1.5
0%
1
0%
0%
2.
3.
0%
0%
4.
5.
Let Y = the number of dropped calls experienced per day by
customers of a particular cell phone provider. Y has the
following probability distribution:
Y
0
1
2
3
Prob
.55
.30
.10
.05
What is the standard deviation of dropped calls per day?
10
1.
2.
3.
4.
5.
1.15
0.853
0.652
2.0
1.5
0%
1.
0%
0%
2.
3.
0%
0%
4.
5.
X and Y are independent random variables with
expected values and standard deviations as shown.
Exp. Value
SD
X
80
12
Y
12
3
What is E(X – Y)?
1.
2.
3.
4.
10
92
68
34
83
0%
1
0%
2
0%
3
0%
4
X and Y are independent random variables with
expected values and standard deviations as shown.
Exp. Value
SD
X
80
12
Y
12
3
What is SD(X – Y)?
1.
2.
3.
4.
5.
9
15
11.62
135
12.37
10
0%
1
0%
0%
2
3.
0%
0%
4
5.
In North Carolina, heights of HS boy basketball players have
mean 74 inches and standard deviation 4.5 inches, while girl
players have a mean height of 70 inches and standard deviation
3 inches. At a mixed 2-on-2 tournament teams are formed by
randomly pairing boys with girls as teammates.
On average, how much taller do you expect the boy to be?
10
1.
2.
3.
4.
5.
4”
2”
7.5”
1.5”
3”
0%
1
0%
0%
2
3
0%
0%
4
5
10
In North Carolina, heights of HS boy basketball players
have mean 74 inches and standard deviation 4.5 inches;
girl players have a mean height of 70 inches and standard
deviation 3 inches. At a mixed 2-on-2 tournament teams
are formed by randomly pairing boys with girls as
teammates.
What is the standard deviation of the difference in the
heights of a boy and girl on a 2-person team?
1.
2.
3.
4.
5.
1.5“
7.5”
5.4”
2.25”
4”
0%
1
0%
0%
2
3
0%
0%
4
5