Page 43 - Pra U STPM 2022 Penggal 3 - Maths (T)

Mathematics Semester 3 STPM Chapter 2 Probability
26. The two way classification table below shows the responses of 100 employees of a company regarding
paying high salaries to directors of companies.
In Favour (I) Against (A) Total

Male (M) 15 45 60
Female (F) 4 36 40

Total 19 81 100
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Suppose one employee is selected at random. Find the probability that the employee selected is,
(a) in favour of paying high salaries to directors.
(b) a male who is in favour of paying high salaries to directors. 2
(c) against of paying high salaries to directors given that this employee is a female. Draw a tree
diagram to illustrate this.
(d) a male given that this employee is in favour of paying high salaries to directors. Draw a tree
diagram to illustrate this.
27. In a cannery, assembly lines A, B and C account for 50%, 30% and 20% of the total output. The
corresponding percentages of the cans from assembly lines that are improperly sealed are listed in the
following table:
Assembly line A Assembly line B Assembly line C

Output 50% 30% 20%
Improperly sealed 0.4% 0.5% 1.1%

Find the probability that an improperly sealed can be discovered at the final inspection of outgoing
products comes from assembly line A.

28. Eighty job applicants are assessed as either good or poor for their aptitude test and communication
skill. The results are recorded in the following two-way classification table.

Good aptitude Poor aptitude

Good communication 24 18
Poor communication 28 10

Calculate the probability that an applicant has
(a) good aptitude test or communication skill,
(b) good aptitude test and communication skill.

29. In a survey on the number of electrical fans in a house, the following probability table is obtained.

Number of fans 0 1 2 3 or more
Probability 0.10 0.28 0.36 0.26

Calculate the probability of a house having
(a) more than one electrical fans,
(b) one or fewer electrical fans.

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02 STPM Math(T) T3.indd 111 28/10/2021 10:21 AM