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# Assignment 2A Total Marks = 65 Please show all your work.

Assignment 2A

Total Marks = 65

Please show all your work. Some questions require you to use graphs, tree diagrams, formulas, and so on that are difficult or impossible to reproduce in word-processing programs, so you will have to print the entire assignment and fill it out and mail it to your tutor. As an alternative to mailing, you might be able to photograph or scan your assignment and submit it through the appropriate drop box. If you do, make sure the material you are submitting is legible.

Question 1

A class of 50 students obtained the following grades in a statistics course:

A 5 B 25 C15 D5

If one student is selected at random, what is the probability that

1 mark           a.   the student obtained a B?

2 marks        b.   the student obtained either a B or a C?

2 marks        c.    the student did not obtain a D?

2 marks        d.   the student did not obtain either a B or a C?

Question 2

A realty company has 100 homes listed for sale. Some of these homes have fireplaces, some have garages, and some have neither. A breakdown is provided in the two-way classification table below.

Fireplace

``` No Fireplace
```

Garage

50

30

No Garage

10

10

a.      If one of these 100 homes is selected at random,

1 mark                   i.    what is the probability that the home selected does not have a fireplace?

3 marks                ii.   what is the probability that the home selected has a fireplace or a garage?

2 marks                iii.  what is the probability that the home selected has neither a fireplace nor a garage?

2 marks                iv.  what is the probability that the home selected has a garage but not a fireplace?

2 marks                v.   what is the probability that the home selected has a garage, given that it has a fireplace?

4 marks        b.   Are the events  Fireplace and  Garage independent? Show your proof.

2 marks        c.    Are the events F and G mutually exclusive? Why?

Question 3

An person has applied for positions at Company A, Company B, and Company C. The probability of obtaining an offer from Company A is 0.4, from Company B is 0.3, and from Company C is 0.6. Assume that the three job offers will be independent.

2 marks        a.   What is the probability that the person will receive job offers from all three companies?

2 marks        b.   What is the probability that the person will receive a job offer from Company B only?

2 marks        c.    What is the probability that the person will receive a job offer from at least one of the three companies?

4 marks        d.   What is the probability that the person will receive exactly one job offer from the three companies?

Hint: Construct a tree diagram.

Question 4

A city council consists of 7 males and 4 females. Two councilors are selected at random to represent the city at an Elton John concert. What is the probability that

2 marks        a.   both councilors are male?

5 marks        b.   one councilor is a male and one a female?

2 marks        c.    at least one councilor is a female?

Note: Express probabilities to 4 decimal places of accuracy.

Hint: Construct a tree diagram.

Question 5

A machine used in a production process is set up correctly 97% of the time. Given that the machine is set up correctly, only 5% of the items it produces are defective, while 95% are not defective. On the other hand, if the machine is set up incorrectly, 60% of the items it produces are defective, while only 40% are not defective.

5 marks        What is the probability that a randomly selected item from the production process will not be defective?

Note: Express probabilities to 4 decimal places of accuracy.

Hint: Construct a tree diagram.

Question 6

5 marks        In a survey of 100 business executives, 60 per cent were male and 40 per cent were female. Seventy per cent of the male executives used a PDA (personal digital assistant). Overall, 60 per cent of the executives used a PDA. Construct a two-way classification table for the survey results.

Question 7

You are given the probabilities listed below.

2 marks        a.   Are A and B independent events? Why or why not?

2 marks        b.   Find P(A and B).

2 marks        c.    Find P(A or B).

2 marks        d.   Find P(A|B).

2 marks        e.   Are B and C mutually exclusive events? Why or why not?

3 marks        f.    Are B and C independent events? Provide a mathematical proof.

Assignment 2A

Total Marks = 65

Please show all your work. Some questions require you to use graphs, tree diagrams, formulas, and so on that are difficult or impossible to reproduce in word-processing programs, so you will have to print the entire assignment and fill it out and mail it to your tutor. As an alternative to mailing, you might be able to photograph or scan your assignment and submit it through the appropriate drop box. If you do, make sure the material you are submitting is legible.

Question 1

A class of 50 students obtained the following grades in a statistics course:

A

5

B

25

C

15

D

5

If one student is selected at random, what is the probability that

1 mark           a.   the student obtained a B?

2 marks        b.   the student obtained either a B or a C?

2 marks        c.    the student did not obtain a D?

2 marks        d.   the student did not obtain either a B or a C?

Question 2

A realty company has 100 homes listed for sale. Some of these homes have fireplaces, some have garages, and some have neither. A breakdown is provided in the two-way classification table below.

Fireplace

``` No Fireplace
```

Garage

50

30

No Garage

10

10

a.      If one of these 100 homes is selected at random,

1 mark                   i.    what is the probability that the home selected does not have a fireplace?

3 marks                ii.   what is the probability that the home selected has a fireplace or a garage?

2 marks                iii.  what is the probability that the home selected has neither a fireplace nor a garage?

2 marks                iv.  what is the probability that the home selected has a garage but not a fireplace?

2 marks                v.   what is the probability that the home selected has a garage, given that it has a fireplace?

4 marks        b.   Are the events  Fireplace and  Garage independent? Show your proof.

2 marks        c.    Are the events F and G mutually exclusive? Why?

Question 3

An person has applied for positions at Company A, Company B, and Company C. The probability of obtaining an offer from Company A is 0.4, from Company B is 0.3, and from Company C is 0.6. Assume that the three job offers will be independent.

2 marks        a.   What is the probability that the person will receive job offers from all three companies?

2 marks        b.   What is the probability that the person will receive a job offer from Company B only?

2 marks        c.    What is the probability that the person will receive a job offer from at least one of the three companies?

4 marks        d.   What is the probability that the person will receive exactly one job offer from the three companies?

Hint: Construct a tree diagram.

Question 4

A city council consists of 7 males and 4 females. Two councilors are selected at random to represent the city at an Elton John concert. What is the probability that

2 marks        a.   both councilors are male?

5 marks        b.   one councilor is a male and one a female?

2 marks        c.    at least one councilor is a female?

Note: Express probabilities to 4 decimal places of accuracy.

Hint: Construct a tree diagram.

Question 5

A machine used in a production process is set up correctly 97% of the time. Given that the machine is set up correctly, only 5% of the items it produces are defective, while 95% are not defective. On the other hand, if the machine is set up incorrectly, 60% of the items it produces are defective, while only 40% are not defective.

5 marks        What is the probability that a randomly selected item from the production process will not be defective?

Note: Express probabilities to 4 decimal places of accuracy.

Hint: Construct a tree diagram.

Question 6

5 marks        In a survey of 100 business executives, 60 per cent were male and 40 per cent were female. Seventy per cent of the male executives used a PDA (personal digital assistant). Overall, 60 per cent of the executives used a PDA. Construct a two-way classification table for the survey results.

Question 7

You are given the probabilities listed below.

2 marks        a.   Are A and B independent events? Why or why not?

2 marks        b.   Find P(A and B).

2 marks        c.    Find P(A or B).

2 marks        d.   Find P(A|B).

2 marks        e.   Are B and C mutually exclusive events? Why or why not?

3 marks        f.    Are B and C independent events? Provide a mathematical proof.

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