You can put this solution on YOUR website! Find the value of z such that approximately 40.15% of the distribution lies between it and the mean.
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On the left side of the distribution that would
leave a tail of (0.50-40.15) = 0.0985
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z = invNorm(0.0985) = -1.2901 on the left side
Or z = 1.2901 on the right side
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Cheers,
Stan H.