Box contains 4 bolts. two of them, labeled #1 and #2 are 5 mm in diameter, and two of them, labeled #3 and #4, are 7 mm in diameter. bolts are randomly selected until a 5 mm bolt is obtained. the outcomes are the sequences of the bolts that can be selected. so one outcome is 1, and another is 342. let x represent the number of bolts selected.
a.find the probability mass function of x.
This can be solved with a tree diagram, or a table, or a simple enumeration. The following is the last method. 1 2 31 32 341 342 41 42 431 432 So there are 10 possible outcomes, out of which 2 have a single pick, 4 have 2 picks, and 4 have 3 picks. The pmf of x is therefore x p 1 1/5 2 2/5 3 2/5
