Results 1 to 2 of 2

Thread: Normal Distribution Probability

  1. #1
    Newbie
    Joined
    Mar 2017
    From
    USA
    Posts
    11

    Normal Distribution Probability

    At a certain college, the average score of a first year student on the verbal part of the SAT is 565, with a standard deviation of 75. If the distribution of the scores is normal, what proportion of that school's first year students have verbal SATs over 650? Under 500?

    For some reason I cannot find the probability of a score under 500. I know the first answer is .129 but it seems that what I'm doing for the second part isn't working. I have P(Z< -87) and I'm getting .1922 but that is not correct.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor

    Joined
    Apr 2005
    Posts
    19,243
    Thanks
    2835

    Re: Normal Distribution Probability

    You are told that the average (mean) is 565 and the standard deviation is 75 so the "standard score" corresponding to 500 is \frac{500- 565}{75}= -0.87 (not "-87"). Using http://math.arizona.edu/~rsims/ma464...ormaltable.pdf, I get P(z< -0.87)= 0.19215 which would round to you "0.1922". How do you know "that is not correct"?
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Normal Distribution using probability
    Posted in the Statistics Forum
    Replies: 1
    Last Post: Nov 24th 2015, 05:10 PM
  2. Probability - Normal Distribution
    Posted in the Advanced Statistics Forum
    Replies: 5
    Last Post: Mar 8th 2010, 12:41 AM
  3. by a normal probability distribution?
    Posted in the Advanced Statistics Forum
    Replies: 0
    Last Post: Oct 2nd 2009, 09:20 PM
  4. Probability + normal distribution
    Posted in the Advanced Statistics Forum
    Replies: 3
    Last Post: Nov 10th 2008, 06:02 PM
  5. Normal Distribution, Std. Dev., & Probability
    Posted in the Advanced Statistics Forum
    Replies: 3
    Last Post: Apr 29th 2008, 03:48 AM

/mathhelpforum @mathhelpforum