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joemama69
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Homework Statement
Q1) It has been observed that contamination level of water [measured in suitable units] in a given waterbody has lognormal distribution with mean = 23.58 units and variance = 3.85 sq units.
What % of samples would indicate contamination level between 20.65 units and 25.85 units ?
Homework Equations
Using the Z table and P((ln(x)-mean)/SD)
The Attempt at a Solution
P((ln(20.65)-23.58)/sqrt(3.85))<=Z<=((ln(20.65)-23.58)/sqrt(3.85)) = phi(-10.36)-phi(-10.47)
Values are way too large... what's going on.