Results 1 to 4 of 4

Math Help - Confidence Interval Help!

  1. #1
    Newbie
    Joined
    Apr 2008
    Posts
    5

    Confidence Interval Help!

    A random sample of 10 miniature Tootsie Rolls was taken from a bag. Each piece was weighed on a very accurate scale. The results in grams were
    3.087
    3.131
    3.241
    3.241
    3.270
    3.353
    3.400
    3.411
    3.437
    3.477
    (a) Construct a 90 percent confidence interval for the true mean weight.
    (b) What sample size would be necessary to estimate the true weight with an error of 0.03 grams with 90 percent confidence?

    This is what I got so far? Im lost!
    3.3115 1.645 (0.131988888)/√10 =
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Aug 2007
    From
    USA
    Posts
    3,111
    Thanks
    2
    You are not lost. You are very close.

    However, I'm a little curious how you managed to get the Standard Deviation right but not the Mean? Try that Mean again.

    For the second part, contemplate 1.645*\frac{0.131988888}{\sqrt{n}} < 0.03

    HOWEVER, and this is a very large HOWEVER, it had better be a VERY LARGE bag of Tootsie Rolls!

    You have a choice...

    Tell me why it needs to be a very large bag, or
    Tell me how you plan to implement the Finite Population Correction Factor.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Apr 2008
    Posts
    5
    Hey ok The mean is 3.305. I dont quit understand this method. The teacher I have hasnt really shown us much on this. I somewhat know how to use this formula but what it actually does I dont know.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by tysupplyguy View Post
    A random sample of 10 miniature Tootsie Rolls was taken from a bag. Each piece was weighed on a very accurate scale. The results in grams were
    3.087
    3.131
    3.241
    3.241
    3.270
    3.353
    3.400
    3.411
    3.437
    3.477
    (a) Construct a 90 percent confidence interval for the true mean weight.
    (b) What sample size would be necessary to estimate the true weight with an error of 0.03 grams with 90 percent confidence?

    This is what I got so far? Im lost!
    3.3115 1.645 (0.131988888)/√10 =
    See this thread: http://www.mathhelpforum.com/math-he...-interval.html
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Confidence Interval
    Posted in the Statistics Forum
    Replies: 5
    Last Post: February 9th 2011, 10:51 PM
  2. confidence interval
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: January 31st 2011, 12:02 PM
  3. Confidence Interval
    Posted in the Advanced Statistics Forum
    Replies: 3
    Last Post: November 28th 2009, 02:50 PM
  4. confidence level and confidence interval?
    Posted in the Advanced Statistics Forum
    Replies: 2
    Last Post: July 12th 2009, 06:59 AM
  5. Confidence Interval
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: April 22nd 2008, 06:55 PM

Search Tags


/mathhelpforum @mathhelpforum