Area Above Negative Z
(A worked Problem:  Procedure explained in more detail in Chapter 7)

Problem:  Suppose that a personality test has:

    Mean = 200
    Standard Deviation = 50

    What is the proportion of people taking this test that score above 180?

I.  First you must convert the original score to a Z score.

II.  Because the Z score is negative and we want to find the area above then:

    A.  We can find the pink shaded area in Column 2 of Table Z = .1554

    B.  Remember that there is .5 on either side of the mean

III.  Therefore the area above = Column 2 + .5 = .1554 + .5 = .6554 or 65.54%

Copyright © 2004 by Mark W. Vernoy