statistics

The time needed to complete a final examination in a particular college course is normally distributed with a mean of 79 minutes and a standard deviation of 8 minutes. Answer the following questions. Assume that the class has 60 students and that the examination period is 90 minutes in length. How many students do you expect will be unable to complete the exam in the allotted time (to 2 decimals)?

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  1. z-score for you time of 90 minutes
    = (90-79)/8 = 1.375

    from tables or from my favourite webpage
    probability not finishing = .0846

    so of 60 students not finishing
    = .0846(60)
    = 5.076

    so 5 students will not finish

    http://davidmlane.com/hyperstat/z_table.html

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  2. time to complete a standardized exam is approximately normal with a mean of 70 minutes and a standard deviation of 10 minutes. Using the 68-95-99.7 rule, if students are given 90 minutes to complete the exam, what percent of students will not finish?

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  3. A researcher is interested in manual dexterity of a group of adults, part of study involves asking the participants to complete a task and you a presented with the following information about the length of time taken to complete it in minutes
    Mean=20
    Sd=4
    Assuming that the data is normally distributed
    What does it tell about a participant that took 25 minutes to complete the task
    If the researcher collected data from 1000 participants, how many people are likely to have completed the task within 16 minutes

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