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Math Help - probability questions... please helP!

  1. #1
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    Exclamation probability questions... please helP!

    Question 3 .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.
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  2. #2
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    Quote Originally Posted by sinni8 View Post
    Question 3 .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.

    Mr F says: You can't do part (a) ...?

    (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.
    For (b) and (c), read this thread: http://www.mathhelpforum.com/math-he...om-sample.html

    It has what you need.
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