3.1.1. What is the probability the person is between 55 and 64 years old or does not have health
insurance?
[2]
3.1.2. If the person is below 55 years of age, what is the probability that he/she has health
insurance
[4] .
3.2. Suppose that the four food inspectors at a food factory are supposed to stamp the
expiration date on each package of food at the end of the production line. John, who
stamps 20% of the packages, fails to stamp the expiration date once in every 200 packages;
Tom, who stamps 60% of the packages, fails to stamp the expiration date once in every
100 packages; Jeff, who stamps 15% of the packages, fails to stamp the expiration date
once in every 90 packages; and Pat, who stamps 5% of the packages, fails to stamp the
expiration date once in every 200 packages.
3.2.1. If a customer picks at random a package of a package, what is the probability that it does
not show the expiration date?
[4]
3.2.2. If a customer complains that her package does not show the expiration date, what is the
probability that it was inspected by John
[4] .
3.3. A diagnostic test for cancer is said to be 98% accurate if a person has the disease. Also, if a
person does not have cancer, the test will report that he or she does not have it with
probability 0.1. Only 0.1% has the disease in question. If a person is chosen at random from
the population and diagnostic test indicates that he or she has cancer, what is the
probability that he or she does, in fact, have cancer.
[4]
QUESTION 4[20 Marks]
4.1. A large industrial firm purchase several new food-processors at the end of each year, the
exact number depending on the frequency of repairs in the previous year. Suppose that
the number of food-processors, X, that are purchased each year has the following
probability distribution:
X
0
1
2
3
p(x)
0.1
0.3
0.4
0.2
If the cost on new food-processors at the end of this year is given by 12000 - SOX2 , in
Namibia Dollars,
4.1.1. how much can this firm expect to spend on new food-processors at the end of this year?
[4]
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