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probability and exponential distribution watch

    • Thread Starter

    Could someone please help me on these two superhard questions:

    On average I recieve one text message every 15.9 hours. Assuming that the time between successive text messages has an exponential distribution, what is the probability that I have to wait between 6 and 34 hours for the next text message to arrive?

    Answer: 0.4646

    I need to schedule an appointment with a student, but before the appointment there is a commitee meeting. The meeting will last a random length of time, exponentially distributed with mean 68 minutes. How many mins after the start of the meeting should I set the appointment if i want to be 87% certain that the meeting is finished before the time scheduled for the appointment?

    Answer: 138.7

    I just don't get what they're asking us to do. Please can someone help me. Arrghhh I hate stats!
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Updated: February 1, 2010

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