According to Engineering News-Record (Dec. 1, 1983), the District of Columbia is now mandating that at least one-half of all the jobs created by city contracts be filled by local residents. Suppose you want to survey jobs created by city contracts after the mandate was issued to determine the level of compliance with the new law. If in fact only 40% of all jobs created by city contracts are filled by local residents:
a) What is the expected number of jobs you would have to survey before you
find one that has been filled by a local resident?

Respuesta :

where  is the probability of success (finding a job filled by a local resident), and  is the probability of failure (not finding a job filled by a local resident).

To find the expected number of jobs you would have to survey before finding one that has been filled by a local resident, we calculate the reciprocal of the probability of finding the first success:

Therefore, you would expect to have to survey approximately 2.5 jobs before finding one that has been filled by a local resident.