1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Population proportion *statistics*

  1. Dec 10, 2006 #1
    1. The problem statement, all variables and given/known data

    Harley-Davidson motorcyles make up 14% of all the motorcyles registered in the United States. You plan to interview an SRS of 500 motorcyle owners.
    a) what the approximate distribution of the proportion of your sample who owns harleys?
    b) Is your sample likely to contain 20% or more who own Harleys? Is it likely to contain at least 15% Harley owners? Do normal probability calculations to answer these questions

    2. Relevant equations
    p-phat = count of success in the sample/n
    p = mean of the sampling distribution
    z =( p-hat - p)/ std.dev

    3. The attempt at a solution
    I believe p = .14. n = 500
    I don't understand what is meant by "approximate distribution of the proportion of your sample who owns harleys".
    If they mean p-hat, would p-hat =(500*14/100) / 500 ? bit that would give me .14..
  2. jcsd
  3. Dec 10, 2006 #2


    User Avatar
    Science Advisor
    Homework Helper

    Hint: The question says "Do normal probability calculations to answer these questions".

    The "exact" probability distribution here is a Binomial distribution. How do you use a Normal distribution to approximate a Binomial distribution?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Threads - Population proportion *statistics* Date
Stats Help! Using Standard deviation and a population Oct 17, 2016
Different types of exponential growth equations? Jul 5, 2015
Population Growth Equation May 11, 2015
Inverse proportion Jan 6, 2015
Number of bacteria in a culture Oct 14, 2014