STAT 200 Week 4 Homework Problems
6.1.2
1.) The commuter trains on the Red Line for the Regional Transit Authority (RTA) in Cleveland, OH,
have a waiting time during peak rush hour periods of eight minutes ("2012 annu
...
STAT 200 Week 4 Homework Problems
6.1.2
1.) The commuter trains on the Red Line for the Regional Transit Authority (RTA) in Cleveland, OH,
have a waiting time during peak rush hour periods of eight minutes ("2012 annual report,"
2012).
a.) State the random variable.
X= waiting time during peak hours
b.) Find the height of this uniform distribution.
1
8−0
=0.125
c.) Find the probability of waiting between four and five minutes.
P(4< X<5)=(5−4)∗0.125=0.125
d.) Find the probability of waiting between three and eight minutes.
P(3< X<8)=(8−3)∗0.125=0.625
e.) Find the probability of waiting five minutes exactly.
P( x=5)=0∗0.125=.0000
6.3.2
Find the z-score corresponding to the given area. Remember, z is distributed as the standard normal
distribution with mean of
0
and standard deviation
1
.
a.) The area to the left of z is 15%.
z-score = -1.036
b.) The area to the right of z is 65%.
z-score = -0.385
c.) The area to the left of z is 10%.
z-score = -1.282
d.) The area to the right of z is 5%.
z-score = 1.645
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e.) The area between
z
and z is 95%. (Hint draw a picture and figure out the area to the left
of the
z
.)
z-score = 1.960 and -1.960
f.) The area between
z
and z is 99%.
z-score = 2.576 and -2.576
6.3.4
According to the WHO MONICA Project the mean blood pressure for people in China is 128 mmHg with
a standard deviation of 23 mmHg (Kuulasmaa, Hense & Tolonen, 1998). Assume that blood pressure is
normally distributed.
a.) State the random variable.
X = the blood pressure of the people in China
b.) Find the probability that a person in China has blood pressure of 135 mmHg or more.
P( x ≥135 )=P(z≥
135−128
23
)
¿ P( z ≥0.30)=1−P(z<0.30)=1−0.6179
= 0.3821
c.) Find the probability that a person in China has blood pressure of 141 mmHg or less.
P( x ≤141)=P(
z≤
141−128
23 )
¿ P(z≤0.565)
=0.7157
d.) Find the probability that a person in China has blood pressure between 120 and 125
mmHg.
P(120< x<125 )=P(
120−128
23
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