Assume that 20 parts are checked each hour and that X denotes the number of parts in the sample of 20 that require
rework. Parts are assumed to be independent with respect to
rework.
(a) If the percentage of parts that require rework remains at
1%, what is the probability that hour 10 is the first sample
at which X exceeds 1?
(b) If the rework percentage increases to 4%, what is the probability that hour 10 is the first sample at which X exceeds 1?
(c) If the rework percentage increases to 4%, what is the
expected number of hours until X exceeds 1?