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Homework Help: Stat Help!

  1. Feb 13, 2006 #1
    EDIT: None of that multiplication rule crap should apply here, D'OH!

    I think this too is another case of the binomial probability; hence:

    [tex] X \sim Bin(10,0.5) [/tex]

    I must evaluate the cases where,


    Ah! The 70% comes into play for the probablity. I want probablity of greater than 70%, or for values of [tex] X \geq .7n [/tex]

    Problem a.)

    From the table,

    [tex] P(X \geq 7) = 1- 0.945 [/tex]


    [tex] P(X \geq 7) = [/tex]5.5%

    Not good chances!

    Part b.)

    [tex] P(X \geq 14) = 1- 0.979 [/tex]

    [tex] P(X \geq 7) = [/tex]2.1%

    Part c.)

    [tex] P(X \geq 35) = 1- 0.99870 [/tex]

    [tex] P(X \geq 7) = [/tex]0.13%

    Part d.)

    [tex] P(X \geq 70) = 1- 1[/tex]

    I begrudgingly made a quick for loop in matlab to calculate Binomial probablity values as high as n=100, with x =70 and p =.5, It spat out 1.000. So,

    The probability of getting a 70% and up is 1-1=0. You ant gota chance.

    My advice, don't guess on your exams, always cheat.
    Last edited: Feb 13, 2006
  2. jcsd
  3. Feb 14, 2006 #2


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    But if you always cheat you will eventually get caught! :)

    Here's an auxiliary problem for you. If the probability of getting caught cheating on any given day is 1 in 100, what is the probability that you will be caught cheating over the course of, say, the next 2 years? The next 5 years? The next 10 years?
  4. Feb 14, 2006 #3
    NOOO! I seriously have TONS and TONS of stat HW due tomorrow and I am trying to learn as I go because my teacher is terrible :mad: I think Im going to get a 3/7 on my HW if im LUCKY. Are my answers right?
  5. Feb 14, 2006 #4


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    I get about 17% for (a) and about 5.8% for (b). I'll give you my other numbers after we figure out why our answers differ.
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