Answer
The event "at least one non word error" means that it contains one or more errors which are not due to misspelling, etc. Probability distribution of x can be given by:
x 1 2 3 4
P(x) 0.2 0.3 0.3 0.1
P(at least one non word error) = 0.2 + 0.3 + 0.3 + 0.1
= 0.9
Work Step by Step
As given above
