In: Statistics and Probability
Suppose the average yearly rainfall in Sydney Australia, is about 137mm and the standard deviation is about 10mm. Use normal approximation to find the probability that the yearly rainfall is less than 110mm.
Let X : The yearly rainfall in Sydney Australia
Given, X follows Normal( = 137, =10)
To find the probability that the yearly rainfall is less than 110mm, i.e., P(X<110)
Using normal appproximation, i.e., Central Limit Theorem, which states that,
Thus,
(from Z-table)
Therefore, the probability that the yearly rainfall in Sydney Australia is less than 110mm is 0.0035
------------------------------------------------------------------------------------------------------------------------------------------
z-table for reference: