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    MsLiz88's Avatar
    MsLiz88 Posts: 1, Reputation: 1
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    #1

    Apr 13, 2011, 12:04 PM
    When applying the standard normal distribution,
    I am trying to find the percentage of people with a higher IQ then 111.

    I have the equation, P(y>111) = P(z >.69)
    At this point I believe I subtract 1 from a decimal number but I don't know what decimal number. It may come from a chart, but I guess I am not familiar with using the chart. After I do the subtraction I can find the percentage. Can anyone show me how to finish my problem?
    Unknown008's Avatar
    Unknown008 Posts: 8,076, Reputation: 723
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    #2

    Apr 13, 2011, 12:27 PM

    It will all depend on what type of z-table you were given. If you have a right-tail end type table, then no, you directly look up the probability/percentage of 0.69 in your table.

    If it's a left-tail end type table, you have to get the probability of:

    P(z < 0.69)

    since that's what you have in your table. Making a sketch tells you that you are looking for the complement of that probability, or that:

    1 - P(z > 0.69) = P(z < 0.69)

    You get P(z < 0.69) in your table, you can find P(z > 0.69). And hence find the percentage.

    Other types of tables will require other approaches.

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