1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    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!

Statistic Question

  1. Nov 1, 2006 #1
    Statistic Question!!

    I have these four questions I'm having trouble solving...
    Could anyone write the solutions, but with steps on how they did it so I can possibly learn! Thanks a lot

    I'm pretty sure they use the binomial or poisson distribution formulas... can't get proper answers


    1. In a large shipment of chips, 5% are defective. What is the probability that exactly two out of a sample of ten are defective?

    2. On average, a system breaks down every 50hrs. Find the probability of more than two break-downs in a 24hr period.

    3. Show that there are more families of 6 children split 4-2 than those with 3 boys and 3 girls.

    4. People arrive at a bank at the rate of 60 per hour. Find the chance of getting 0,1,2 or 3 in the next minute.
     
  2. jcsd
  3. Nov 2, 2006 #2
    This is how I would to do it.
    1. Let p=0.05 q=.95. Do a binomial of (10 choose 2)x p^2 x q^8
    You need the number of ways to arrange 2 defects in 10 trials multiplied by the probabilty of each event, ie. two defects.
    2. Need to convert the Lamba given to one that represents a breakdown per 24 hr period. Here Lamda is 1 per 50 hour period. That represents a lamda of 12/25 per 24 hr period. Now find the probability of no breakdowns, 1 breakdown, and 2 breakdowns in a 24 hr period and then subtract that from 1 leaves probability of more than 2.
    3. No sure, but on first glance seems like showing that 6 choose 4 is larger than 6 choose 3. I would check on this though.
    4. Same as 2. Convert the lambda to a mean for 1 minute and use Poisson distribution.
     
  4. Nov 2, 2006 #3
    4. Same as 2. Convert the lambda to a mean for 1 minute and use Poisson distribution.

    so would lambda be 1/60 and after I find the chance of getting 3 in the next minute... thats the chance of 3 not coming in the next minute? so I subtract that from 1 to get 3 coming in the next minute?

    Thanks a lot for the help
     
  5. Nov 2, 2006 #4
    Yeah use lamda as 1/60. Then it is just a case of finding probability for X=0 X=1 X=2 X=3. 1-P(x=3) is the chance of any number of people in the next minute other than 3 people, but they are not asking you for that. Just plug in x=i i=0,1,2,3 and youre done. You should have four different probabilities corresponding to each part.
     
  6. Nov 2, 2006 #5
    THANKS!
    I get it...
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Statistic Question
  1. Statistics Question (Replies: 0)

  2. Statistics questions (Replies: 5)

  3. Statistics question (Replies: 0)

  4. Statistics question :/ (Replies: 9)

  5. Question in Statistics (Replies: 3)

Loading...