You can put this solution on YOUR website! Find the value of z such that approximately 27.64% of the distribution lies between it and the mean.
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left tail = 0.5000-0.2764 = 0.2236
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z-value = invNorm(0.2236) = -0.7601
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Also, by symmetry, z = +0.7601
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Cheers,
Stan H.