### Home > CCA2 > Chapter 12 > Lesson 12.1.3 > Problem12-48

12-48.
1. Governments and security companies are coming to rely more heavily on facial recognition software to locate persons of interest.

2. Consider a hypothetical situation. Suppose that facial recognition software can accurately identify a person 99.9% of the time, and suppose the suspect is among 200,000 facial images available to a government agency. When the software makes a positive identification, what is the probability that it is not the suspect? Homework Help ✎

1. Make a model for this situation.

2. If a person has been identified as the suspect, what is the probability that he or she is not actually the suspect?

Use the model at right as a starting point.
Complete it by including the probabilities.

P(suspect) = 1/200,000. P(ID is correct) = 0.999.
P(not the suspect) = ?. P(ID is not correct) = ?.

$\text{Probability} =\frac{\text{\# of desired outcomes}}{\text{\# of possible outcomes}}$

The desired outcome is a person who is not the suspect being incorrectly identified, or situation D.
The possible outcomes are situation D and the suspect being correctly identified, or situation A.