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  1. timmy720 timmy720 is offline

    Hatboro, PA
    United States

    Posts: 211
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    Apr 16th, 2008 (4/16/2008 4:40pm)

    How would I do a problem like this using my graphing calculator?

    A department of Transportation report about air travel found that, nationwide, 76% of all flights are on time. Base the following questions on 1000 randomly selected flights.

    Find all probabilities and round to the tenth of a percent.

    a) How many flights would you expect to be late? Obv that answer is 24 percent

    b) What would be the standard deviation

    c) What is the probability you will have exactly 800 flights on time?

    d) What is the probability you will have 200 or less flights that are late?

    e) What is the probability you will have more than 850 on time?

    Any help would be greatly appreciated
     
  2. jtown1010 jtown1010 is offline

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    Apr 16th, 2008 (4/16/2008 4:44pm) in reply to timmy720

    LOL there's so many calculations that you need to do for C-E, at least you get to round to the nearest decimal on B though, I might could guess that in my head, .3?
  3. timmy720 timmy720 is offline

    Hatboro, PA
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    Apr 16th, 2008 (4/16/2008 4:51pm) in reply to jtown1010

    How would I figure it out though I know how to do standard deviation when you have a bunch of different numbers but not like this. And all numbers can be rounded to the 10th of a percent.
     
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  4. WeWaysAwIn WeWaysAwIn is offline

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    Apr 16th, 2008 (4/16/2008 4:53pm) in reply to timmy720

    a. 1-.76 =.24

    b. sqrt (1000x.76.24)

    c. binompdf(1000,.76,800)

    d. binomcdf(1000,.76,799)

    e. 1- [binomcdf(1000,.76,850)]

    binompdf and binomcdf are in 2nd vars on TI-83 and 84s if I remember right.
  5. timmy720 timmy720 is offline

    Hatboro, PA
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    Apr 16th, 2008 (4/16/2008 5:06pm) in reply to WeWaysAwIn

    I have a TI-83 plus. For b is that 1k times .76 and 1k times .24 of is it 1k times .76.24? and could you explain why i would do all this and how to plug in the terms for c and d.
     
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  6. WeWaysAwIn WeWaysAwIn is offline

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    Apr 16th, 2008 (4/16/2008 5:10pm) in reply to timmy720

    yeah its 1k times .76 times .24 all square rooted. the formula for variance of a binomial variable in your textbook should be np(1-p) and standard deviation is the square root of the variance

    binomial pdf gives you the probability of the exact value

    binomialcdf gives you the probability of that value AND all values below it

    they are entered in the order (sample size, probability of a success, successes)

    so binomcdf (10,.8,8)

    is the probability of getting 0,1, 2, 3, 4, 5, 6, 7 or 8 in a sample of 10 with p=.8

    going to dinner gl with your homework. pm me if this is confusing.
  7. curiousgeorge curiousgeorge is offline baby duck hat

    Las Vegas, NV
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    Apr 16th, 2008 (4/16/2008 7:12pm) in reply to WeWaysAwIn

     
    Originally Posted by WeWaysAwIn View Post


    yeah its 1k times .76 times .24 all square rooted. the formula for variance of a binomial variable in your textbook should be np(1-p) and standard deviation is the square root of the variance

    binomial pdf gives you the probability of the exact value

    binomialcdf gives you the probability of that value AND all values below it

    they are entered in the order (sample size, probability of a success, successes)

    so binomcdf (10,.8,8)

    is the probability of getting 0,1, 2, 3, 4, 5, 6, 7 or 8 in a sample of 10 with p=.8

    going to dinner gl with your homework. pm me if this is confusing.

    listen to this guy, he knows his shit.
  8. WeWaysAwIn WeWaysAwIn is offline

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    Apr 16th, 2008 (4/16/2008 7:28pm) in reply to timmy720

    w1060waddison on aim if you're still looking at this timmy
  9. jtown1010 jtown1010 is offline

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    Apr 16th, 2008 (4/16/2008 7:31pm) in reply to WeWaysAwIn

    I added you, will you be my "Math Guru"?

    Por Favor...
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