Normal Distribution

[star.0909]

The time needed to complete a final examination in a particular college course is normally distributed with a mean of 160 minutes and a standard deviation of 20 minutes. Answer the following questions:

1. What is the probability of completing the exam in 120 minutes or less? (2 marks)
2. What is the probability that a student will complete the exam in more than 120 minutes but less than 150 minutes? (2 marks)
3. What is the probability that a student will complete the exam in more than 100 minutes but less than 170 minutes? (2 marks)
4. Assume that the class has 120 students and that the examination period is 180 minutes in length. How many students do you expect will be unable to complete the examination in the allotted time? (4 marks)
5. I am so lost of where to start for this question

 

[Deleted member 4993]

The time needed to complete a final examination in a particular college course is normally distributed with a mean of 160 minutes and a standard deviation of 20 minutes. Answer the following questions:

1. What is the probability of completing the exam in 120 minutes or less? (2 marks)
2. What is the probability that a student will complete the exam in more than 120 minutes but less than 150 minutes? (2 marks)
3. What is the probability that a student will complete the exam in more than 100 minutes but less than 170 minutes? (2 marks)
4. Assume that the class has 120 students and that the examination period is 180 minutes in length. How many students do you expect will be unable to complete the examination in the allotted time? (4 marks)
5. I am so lost of where to start for this question

Please show us what you have tried and exactly where you are stuck.

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Please share your work/thoughts about this problem.

 

[Dr.Peterson]

The time needed to complete a final examination in a particular college course is normally distributed with a mean of 160 minutes and a standard deviation of 20 minutes. Answer the following questions:

1. What is the probability of completing the exam in 120 minutes or less? (2 marks)
2. What is the probability that a student will complete the exam in more than 120 minutes but less than 150 minutes? (2 marks)
3. What is the probability that a student will complete the exam in more than 100 minutes but less than 170 minutes? (2 marks)
4. Assume that the class has 120 students and that the examination period is 180 minutes in length. How many students do you expect will be unable to complete the examination in the allotted time? (4 marks)
5. I am so lost of where to start for this question

I'd say the place to start is to identify \(\mu\) and \(\sigma\) in the problem, and then for each question identify one or more values of \(x\).

Then write out the formula for \(z\) and calculate it in each case.

Then you'll have to show us what you get, and what method you have for finding the probability associated with each \(z\): a table, memorized values, software, or something like that.

To tell the truth, though, the place to start was to read the material you were given, working through examples, and then try it out on ungraded exercises for which answers are provided, rather than wait until now to wonder how to start.