28 Dec Take advantage of

Unit 3 Discussion 1

Probability and statistics allow us to make decisions when dealing with uncertain variables. For example, assume you are the network administrator of a large firm and have ordered 100 RAID (redundant array of independent disks) devices. You would like to make sure all of the RAIDs work before sending them to different departments. But you do not have time to check all of the devices. If you check some of them and show they work, how confident could you be that all 100 devices work?

Of course, testing all of the RAIDs would be the best way to be confident, but assume you do not have the time. If you only have time to check 5 of the 100, and none of the 5 are defective, how confident would you be that none of the other microprocessors are defective (that is, all 100 devices are fully functional)?

Answer the following questions, which will help you understand the problem. Explain each question and your answer:

1. How can you use discrete probability to calculate the probability of testing 5 devices such that all 5 end up being nondefective RAIDs, given there are 20 defective RAIDs total of the original 100 RAID devices?

2. What is the sample space in this problem?

3. Is this a ratio of combinations or permutations problem? Explain why and show an example. Hint: Read section 6.5 and see Example 6.5.4 in your textbook.

4. Assume there are exactly 5 defective RAIDs out of the 100 RAID devices. What is the probability of testing 20 RAIDs at random and finding all of them nondefective?

Review the Discussion Participation Scoring Guide prior to posting.

Unit 3 Discussion 2

This discussion allows you to work with your peers to complete and understand the assigned problem set for this unit. Remember, two initial posts and two response posts are required. Further posts are optional and recommended:

• For the first post, select a problem from this unit’s problem set, write it out fully, solve it fully, and post it.

• The second post can be a problem you cannot solve or another fully solved problem from the problem set. If there is a problem in the problem set that you are confused about, write it out fully and show any work that you have started. Note that you are stuck and ask for help. If you are able to solve every problem in the set without difficulty, post at least one other fully solved problem from the set as your second post.

• The third and fourth posts are responses. Response guidelines are provided below and in every discussion.

Take advantage of this discussion area to work together as a class on the problem set. Post as many problems as you can and review as many of your peers’ posts as you can. Ask questions. Offer answers. If you are stuck on a problem, post your question. Working as a team will help each person gain a better understanding of the problem set and the concepts covered in this unit. Although the problem sets are not graded they will help you prepare for the quizzes in this course.

Response Guidelines

The third and fourth posts, the response posts, are your chance to help your peers. Explore the posts made by your peers and find people who are stuck. Help at least two peers through the problems they are stuck on. If you are unable to locate a peer who is stuck, you may instead choose a peer post, write out your solution to the same problem, and compare solutions and methods. The goal of this area is for the entire class to work together as a group on the entire problem set. You are also expected to complete and understand the problem set on your own in preparation for the quizzes and final exam.