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The area under the entire normal
curve is 1. we want the z scores so that 0.88
is the area between those points under the curve then this means that 1-0.88=.12
is the distribution's area not between -z and z.

Since graph is symmetrical with
respect to z=0 therefore half of this area will be towards +z & half will
be towards –z hence Find the z score for
0.12/2 = .06 is the area to the right of
z.

from table of the standard normal
distribution.

z=1.55 gives very close value =
0.06057 hence

88% of the distribution's area lies between z=-1.55 and z=1.55

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