Question

Devore Ch 1, problem 3. For each part, a, and b, state two answers that are not given in the back of the book. They can be similar, but have to be different. For example, in Part a, one answer is:  “How likely is it that more than half of the sampled computers will need or have needed warranty service?” An acceptable answer might be:  “How likely is it that more than 75% of the sampled computers will need or have needed warranty service?” Of course, now that I’ve given you that answer, you can’t use it. ^_^

HERE IS THE problem

3. Consider the population consisting of all computers of a certain brand and model, and focus on whether a computer needs service while under warranty. a. Pose several probability questions based on selecting a sample of 100 such computers. b. What inferential statistics question might be answered by determining the number of such computers in a sample of size 100 that need warranty service?

Answer 1

a. When 100 computers of a certain brand and model are selected, the probability questions might be

I. Based on Historical numbers

1. How likely is it that less than 50% (or any such percentage of interest like 30%, 10% etc.) of the sampled computers have needed warranty service in the past

2. How likely is it that more than 50% (or any such percentage of interest like 70%, 90% etc.) of the sampled computers have needed warranty service in the past

II. Based on Future Expectation

3. How likely is it that a particular sampled computers that has not needed any warranty service in past will need it within next 3 months (or any other timeline such as 6 months, one year etc)

4. How likely is it that a particular sampled computers that has needed warranty service in past will need it again within next 3 months (or any other timeline such as 6 months, one year etc)

III. Based on Customer Behavior, Statistics w.r.t. Computer Warranty etc.

5. How likely is it that a computer from the sampled computers that actually needed warranty service was not availed by the customer

6. How likely is it that two computers out of the sampled computers that needed warranty service required it for the same reason of malfunction

7. How likely is it that two computers out of the sampled computers that needed warranty service required it for the different reasons of malfunction

b. Let the numbers of computers out of 100 that need warranty service be N. The inferential statistics questions that can be answered are

1. How likely is it that the N computers who will be serviced will not need another service for next 1 year (or any other tilmeline such as 2 or 3 or 5 years etc)

2. How likely is it that the (100-N) computers who do not need servide right now will need it after 1 year (or any other tilmeline such as 2 or 3 or 5 years etc)

3. How likely is it that if another batch of 100 computers is selected, the number of computers that will need to be servied or more than (or less than) N?

4. How likely is it that if another batch of 1000 computers is selected, the number of computers that will need to be servied or more than (or less than) 10N?