1. Discrete Variables Classes
Defectives
The presence of a non-conformity ruins the entire unit – the unit is defective
Example – fuses with disconnects
Defects
The presence of one or more non-conformities may lower the value of the unit, but does NOT render the entire unit defective
Example – paneling with scratches

2. Binomial Distribution
Sequence of n trials
Outcome of each trial is “success” or “failure”
Probability of success = p
r.v. X - number of successes in n trials
So: where
Mean: Variance:

3. Binomial Distribution Example
A lot of size 30 contains three defective fuses.
What is the probability that a sample of five fuses selected at random contains exactly one defective fuse?
What is the probability that it contains one or more defectives?