Normal and Lognormal Distributions

• Need to know mean, and standard deviation

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Example 1

• Step One, Standardize

• Now, need to check the Normal Distribution Table
• Find the Value. The table will tell you everything from the “Left side” to the number you want, and here, we have the right side.
• So, we need to do 1 — the table value.
• If you get a negative number, just use the equivalent positive number, and use the same process.

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Normal Distributions are really helpful, but they are not without faults!

• There is a very small chance, (about 1/100,000), but we can end up arriving at work before we’ve even left in the last example.
• It’s a very small chance, but still a problem with the normal.

Lognormal Distribution

• If X is lognormally distributed, then $l{n}_X$ is normally distributed

Lognormal Distribution

Example 2