Results 1 to 2 of 2

Math Help - 5.5 help teacher is a mofe

  1. #1
    Blockface
    Guest

    5.5 help teacher is a mofe

    A drug company tested a new drug on 250 pigs with swine flu. Historically, 20% of pigs contracting swine flu die from the disease. Of the 250 pigs treated, 215 recovered. Estimate the probability that this result is by chance.

    Please somebody help. the class average for our classes last unit test was 14%. Our teacher is such a mean sob he says its our fault...this is a question on the make-up test and i still dont get it. Also, share your horrible teacher stories, itll be hilarious stuff.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by Blockface
    A drug company tested a new drug on 250 pigs with swine flu. Historically, 20% of pigs contracting swine flu die from the disease. Of the 250 pigs treated, 215 recovered. Estimate the probability that this result is by chance.
    The number that die has a binomial distribution, but here we have moderately
    large numbers so we will use the normal approximation to the binomial distribution.

    Expected number of deaths in 250 cases is \mu=0.2\times 250=50.

    The standard deviation of a binomially distributed random variable is \sqrt{Np(1-p},
    where N is the number of trials ( N=250 in this case), p is the probability
    of the outcome of interest on a single trial (in this case p=0.2). So the
    standard deviation of the number of deaths is: \sigma=\sqrt{250\times 0.2 \times 0.8}\approx 6.32

    So now the question is: what is the probability of 35 or fewer deaths
    happening by chance assuming the treatment has no effect.

    We work with 35.5 or fewer to allow for the continuous nature of the normal
    approximation, and so the critical z-score we are interested in is:

    z=(35.5-50)/6.32 \approx -2.29

    This is looked up in a table of the cumulative standard normal distribution to
    give:

    P(\mbox{35 or fewer deaths given no treatment})\approx 0.011,

    or about 1.1 \%

    RonL
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 4
    Last Post: December 7th 2009, 11:38 AM
  2. has my teacher been wrong here..
    Posted in the Differential Equations Forum
    Replies: 0
    Last Post: August 28th 2009, 02:43 AM
  3. “Please teacher why should I do Maths”
    Posted in the Math Topics Forum
    Replies: 4
    Last Post: July 3rd 2009, 10:52 AM
  4. Is there a teacher in the house?
    Posted in the Algebra Forum
    Replies: 1
    Last Post: April 6th 2009, 05:54 PM
  5. Teacher cant even do this.......
    Posted in the Calculus Forum
    Replies: 2
    Last Post: March 31st 2008, 05:43 AM

Search Tags


/mathhelpforum @mathhelpforum