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Probability questions

  1. Sep 15, 2008 #1
    probability questions plz help!!

    An engineer wishes to estimate the mean setting time of
    a new cement mix used in highway spot repairs. From a record of setting times
    for 10 spot repairs he obtain
    x = 25; 25; 24; 23; 25; 26; 23; 24; 22; 23
    minutes, respectively.
    (a) Find the mean and standard deviation of the setting time.

    (b) Find a 95% confidence interval for the mean setting time if the standard deviation
    is known to be ¾ = 1:5 min: Assume a normal distribution
    (c) Find a 95% confidence interval for for the mean setting time if the standard
    deviation is unknown.
     
  2. jcsd
  3. Sep 15, 2008 #2

    tiny-tim

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    Science Advisor
    Homework Helper

    Welcome to PF!

    Hi sinni8! Welcome to PF! :smile:

    Show us what you've tried, and where you're stuck, and then we'll know how to help. :smile:
     
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