Question

Three invoices prepared by Shanty , Jenny and Sherry . A sample of 500 invoices are selected . Two hundred were prepared by Shanty , 120 by Jenny and 180 by Sherry . The error rates of Shanty , Jenny and Sherry were found to be 2 % , 3 % and 4 % respectively . From the sample of 500 invoices , one was selected . a . Sketch a Tree Diagram based on the information given in the question b . Compute the probability that invoice contains error ?

Answer 1

a. Tree Diagram:

b. Probability that invoice contains error:

$P(E)=P(E∣A)P(A)+P(E∣L)P(L)+P(E∣J)P(J)$

$P(E)=0.10+0.0072+0.014=0.1212$