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-   -   what's the probability, the sample mean for the 16 hour long periods is less than 47? (https://www.askmehelpdesk.com/showthread.php?t=510349)

  • Sep 23, 2010, 10:51 PM
    rishi27
    What's the probability, the sample mean for the 16 hour long periods is less than 47?
    The outside “clip‐on” lanes of the Auckland Harbour Bridge are to be closed to heavy vehicles, due to
    structural damage.
    Suppose in order to understand the amount of cargo being transported over the bridge that Land
    Transport monitored the traffic for 16 randomly selected one hour periods. The number or trucktrailers
    were counted for each one hour period and the sample mean x calculated.
    Assume the number of truck‐trailers crossing the bridge per hour is normally distributed with a mean
    50 and standard deviation of 8.
  • Sep 24, 2010, 08:49 AM
    Unknown008

    Define your variable.

    Let X be the number of trucks/trailers using the bridge in the 16 hours sample.

    X ~ N(50, 8^2)

    You are to find P(X < 47).

    Convert this X value to a z value by using:



    Then look up your z table for the probability associated with this z value.
  • Sep 24, 2010, 05:15 PM
    rishi27
    Comment on Unknown008's post
    Extremely helpful in confirming my analysis of problems. Thank you

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