In: Math
Poissson distribution
In order to control the polishing quality of a lens, a certain company is used to finish the number of spots on the surface considering the defective lens if 3 or more spots appear on it. The average rate is 2 defects per cm2. Calculate the probability that a 4cm2 lens will not be classified as defective.
Solution:
we are given that: In order to control the polishing quality of a lens, a certain company is used to finish the number of spots on the surface considering the defective lens if 3 or more spots appear on it.
So if there are 2 or fewer spots , then it is not classified as defective.
We have the average rate is 2 defects per cm2, then average rate of defective per 4 cm2 lens will be 2 * 4 = 8 defects per 4 cm2. That is:
We have to find:
P( 4 cm2 lens will not be classified as defective)=.............?
That is:
P( number of defects are less than or equal to 2 ) = ..........?
Using Poisson probability distribution:
Use excel or scientific calculator to find e-8 = 0.0003355
Thus the probability that a 4cm2 lens will not be classified as defective is 0.013754