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Help with Expected Value and Variance?
A certain typing agency employs two typists. The average number of errors per article is 3.8 when typed by the first typist and 2.3 when typed by the second. If your article is equally likely to be typed by either typist, find the probability that it will have no errors.
I understand 3.8(.5) + 2.3(.5) for Expected value, but how do I determine probability of zero errors?
1 Answer
- LeonardLv 77 years ago
You could apply the Poisson prob., where the mean for the typists would be 3.8 and 2.3.
X=# errors; P(X=0)=(3.8)^0 e^(-3.8)/ 0!=.0224 for 1st typist;
similarly, P(X=0)=.1003 for the 2nd typist.
So prob. of 0 errors is 1/2(.0224 + .1003)=.06135.