SOLUTION: Textbook authors and publishers work very hard to minimize the number of errors in a text. However, some errors are unavoidable. Mr. J. A. Carmen, statistics editor, reports that t

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Question 1150893: Textbook authors and publishers work very hard to minimize the number of errors in a text. However, some errors are unavoidable. Mr. J. A. Carmen, statistics editor, reports that the mean number of errors per chapter is 0.8 . What is the probability that there are less than 2 errors in a particular chapter?
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

Let the event an error appearing in a chapter be a success.
Let "x" represent the number of success.
The number of errors in a chapter can be either 0,1,2,...
==> "x" can carry the values 0,1,2,3,...
==> "x" is a discrete random variable with range = { 0,1,2 },..... [Countably infinite]

The probability distribution of "x" is a Poisson+distribution.
Since there are a large number of trials all of which are identical and independent with only two possible outcomes in each trial, either a success (there being an error) or a failure (there not being an error), with the probability of success in all the trials remaining the same all thought.

The probability function of a Poisson distribution
==> P%28X+=+x%29+=+%28e%5E%28-m%29+%2A+m%5E%28x%29%29%2Fx%21

Parameter of the distribution
==> Mean of the distribution
==> Mean number of errors per chapter =0.8+
==> m = 0.8

Therefore P%28X+=+x%29+=+%28e%5E%28-0.8%29+%2A+%280.8%29%5E%28x%29%29%2Fx%21

Probability that there are less than 2 errors in a chapter
==>+P%28x+%3C+2%29
= P%28x=0%29+%2B+P%28x=1%29
=
= %28e%5E%28-0.8%29+%2A+1%29%2F1+%2B+%28e%5E%28-0.8%29+%2A+%280.8%29%29%2F1
= e%5E%28-0.8%29+%2B+%28e%5E%28-0.8%29+%2A+%280.8%29%29
=+e%5E%28-0.8%29+%28+1+%2B+0.8%29
= e%5E%28-0.8%29+%281.8%29
=0.8088 approximately