Results 1 to 2 of 2

Math Help - Hypothesis testing and confidence intervals

  1. #1
    Newbie
    Joined
    Feb 2011
    Posts
    3

    Hypothesis testing and confidence intervals

    Here is the question:
    Suppose that we are interested in buying ball bearings from a certain manufacturer. We require very precisely manufactured ball bearings, and so we decide to investigate this manufacturer's output. The manufacturer insists that at least 98% of their manufactured bearings will be within our acceptable tolerance limits.
    We decide to test this claim. Let's test the claim that the population proportion that are within tolerance limits is .98, against the alternative that the true proportion is less than .98.
    Suppose we draw a random sample of 1000 of the ball bearings, and find only 912 are within the acceptable tolerance limits.


    #15. What is a 95% confidence interval for the proportion of bearings that are within tolerance limits?
    A) .912 .018
    B) .912 .021
    C) .912 .024
    D) .912 .027
    E) .912 .030

    #16. Which one of the following represents the appropriate hypotheses?
    A) Ho: p=.98 Ha: p>.98
    B) Ho: p-hat =.98 Ha: p-hat <.98
    C) Ho: p=.98 Ha: p doesn't equal .98
    D) Ho: p=.98 Ha: p<.98


    I don't understand how you can do them without standard deviation. Some help in starting the question would be great.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor matheagle's Avatar
    Joined
    Feb 2009
    Posts
    2,763
    Thanks
    5
    use \hat p \pm Z_{\alpha/2}\sqrt{{\hat p\hat q\over n}}

    where z=1.96

    The st deviation of \hat p is \sqrt{{pq\over n}}
    and you don't know p or q, so you estimate them.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Hypothesis Testing and confidence interval questions
    Posted in the Advanced Statistics Forum
    Replies: 0
    Last Post: October 10th 2010, 09:28 AM
  2. Confidence intervals, hypothesis testing etc.
    Posted in the Advanced Statistics Forum
    Replies: 0
    Last Post: May 8th 2010, 06:02 PM
  3. Hypothesis testing and confidence intervals.
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: April 22nd 2010, 03:59 PM
  4. Hypothesis testing ad confidance intervals
    Posted in the Advanced Math Topics Forum
    Replies: 3
    Last Post: June 15th 2008, 07:19 AM
  5. Replies: 2
    Last Post: April 2nd 2008, 07:29 AM

Search Tags


/mathhelpforum @mathhelpforum