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Finding a Z-score from a specified Area to the Left
Example: Find the Z-score such that the area to the left of Z-score is 0.32.
This is
called an inverse normal problem and the command invNorm( area,
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)
is used. In this type of problem, an area under the normal curve is given and
you are asked to find the corresponding Z-score. In this example, the area
given is the area to the left of a Z-score. The area is 0.32. (The area value
that you enter into the TI-83 must always be area to the left of a Z-score).
To find the Z-score corresponding to left area of 0.32, press 2nd [DISTR] and select 3:invNorm( and type in .32 , 0 , 1 ) and press ENTER.
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The Z-score of -.47 has an area of 0.32 to the left.