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Math Help - Probability question help!

  1. #1
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    Probability question help!

    1. Assume 60% of population have DVD and 35% have iPod. If someone is selected at random what is probability that they either have a DVD or iPod?
    2. In a factory, machines of type A produce 30% of the output, machines of type B produce 25%, and machines of type C produce 45% of the output. On average, 2% of the produce from the machines of type A is defective, with 3% defective from type B and 4% from type C. Calculate the probability that an item of output from the factory chose at random is defective. If a defective item is chosen calculate the probability that it was made by a machine of type C?
    3. The police discover a murder victim at 6:00am. The body temp of victim is measured then found to 28 deg C. A doctor arrives on the scene of the crime 60 minutes later and measures the body temp again. It is found to be 24 deg C. the temp of the room remains constant at 12 deg C. the doctor knowing that normal body temp is 37 deg C, is able to estimate the time of death of the victim. If the cooling process is modelled by the equation θ = θ0 е-kt, where θ is the excess temp over room temperature, use this model to estimate the time of death.
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  2. #2
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    Re: Probability question help!

    1) 0.6*0.65+0.35*0.4
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  3. #3
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    Re: Probability question help!

    explain how you got to this answer
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  4. #4
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    Re: Probability question help!

    Quote Originally Posted by Rizwan123 View Post
    1. Assume 60% of population have DVD and 35% have iPod. If someone is selected at random what is probability that they either have a DVD or iPod?
    That question is so poorly worded that I doubt that it can be answered. We do not know if the two groups are disjoint. If not, we donít know how they intersect. Therefore,
    Quote Originally Posted by wnvl View Post
    1) 0.6*0.65+0.35*0.4
    has no meaning whatsoever.
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  5. #5
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    Re: Probability question help!

    they are disjoint,
    could you please explain how to do it. what about 2 and 3
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    Re: Probability question help!

    Quote Originally Posted by Rizwan123 View Post
    they are disjoint,
    Why was that not stated in the OP?
    So 0.05 have neither.
    Thus 1-0.5 have at least one.
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  7. #7
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    Re: Probability question help!

    that answer has no meaning, explain how you arised to it.

    is there a way of wolfram alpha calculating it?
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  8. #8
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    Re: Probability question help!

    Quote Originally Posted by wnvl View Post
    1) 0.6*0.65+0.35*0.4
    =P(person has no IPOD)*P(person has DVD)+P(person has IPOD)*P(peson has no DVD)

    clear now?

    I assume you mean people that have a DVD or an IPOD and not both.
    Last edited by wnvl; April 25th 2012 at 04:02 PM.
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