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hmdp4

  • 3 years ago

Standard normal distribution question!! assume that adults have IQ scores that are normally distributed with a mean of 100 and a standard deviation 20. Find P15, which is the IQ score separating the bottom 15% from the top 85%. how do i find this!

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  1. CliffSedge
    • 3 years ago
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    You're looking for the 15th percentile. You need to find the z-score corresponding to a proportion/probability of 0.1500, then use the z-score formula to solve for x.

  2. CliffSedge
    • 3 years ago
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    This site is rather good for straight-forward notes and formulas: http://stattrek.com/probability-distributions/standard-normal.aspx?Tutorial=Stat

  3. CliffSedge
    • 3 years ago
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    |dw:1349413921591:dw|

  4. CliffSedge
    • 3 years ago
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    Here's a Z-table if you need it: http://www.math.unb.ca/~knight/utility/NormTble.htm

  5. SWAG
    • 3 years ago
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    nICE WORK

  6. hmdp4
    • 3 years ago
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    i still dont understand.

  7. CliffSedge
    • 3 years ago
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    Do you have a calculator with an inverse normal function?

  8. CliffSedge
    • 3 years ago
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    If not, you'll need to use that z-table that I linked to. Find the P=0.1500 in the body of the table and read across to the margins to find the associated Z-score. Sometimes you have to estimate between two values and pick the closest one. follow the stattrek.com link to get the z-score formula, plug in your z, µ, and σ, and solve for x.

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