Question

70% of new employees take a learning lessons.
During first month of work they have probability of 0.04 to make mistakes while those who didn't take lessons (30%) have probability of 0.09.
Given that an employee didn't make mistakes in his first month, what is the probability that he had token lessons

Answer 1

look at 1000 new employees

700 took lessons
... 28 made mistakes in 1st month

300 did not take lessons
... 27 made mistakes in 1st month

[1000 - (28 + 27)] did not make a mistake

[700 - 28] took lessons

Answer 2

200