tailieunhanh - Project Management Professional-Chapter 20

APPENDIX: PROBABILITY DISTRIBUTIONS In the discussion so far, I have tried to sound less like a statistician and more like a project management practitioner. The material I have covered here is mainly practical. But there are a few more things we should discuss if we are going to use any of the many statistical packages that are available for project management. Many of these software packages require making decisions on the type of distributions to use, so it is important to know the differences. A probability distribution is a list of all the possibilities that could occur and a probability associated. | APPENDIX PROBABILITY DISTRIBUTIONS In the discussion so far I have tried to sound less like a statistician and more like a project management practitioner. The material I have covered here is mainly practical. But there are a few more things we should discuss if we are going to use any of the manystatisticd packages thatare available for projectmgm j emee t. Mrniyvf thsge softwatnpackanss require mdemg decisions nnihe typg ofeiutributioca tsw tmeoatakttogenwtaa differences Aprobnbiiity diktrtgrtignis aiigo of ailits eossibihtierihatcouidoesur and a asubafilltnassociateg ndth aachofihem. Thee EvenDighribution The even distribution is perhaps the easiest to understand. In the even distribution there is an even chance that any of the possibilities will occur. A good example is the rolling dieisnotloaded there is an equal chancathagany ot tteposgiblenumbeatcghld comckaceuh-Thy a nssiyil ties areS 3 4 5 ork. Agyoucgn saefrom thn plot Sn figure A-i ehnre is an equsl chcrce gfrallmgai 2 3 4 5 oeg. Binomial Distribution As we move into more complex distributions the calculation of the probabilities becomes more complex. The binomial distribution describes the probabilities of all of the possible oudeomes ofa .scricsofeo rimerits where each experiment iridenticf egeim ssiCee ouicstmes. Tithe pgbtscider hsstributianic atg tm r veoieat maagkementbecanse there ere menf rieuations Sn eiek mcnagement wher5tnnrease twoposeiHe outcomesgsitcœss end gmiiure. In ordae to use sSer binoaesci gisttigntecn thraecgnditioiir musibe met. 375 376 Appendix Probability Distributions FigureA-1. Even distribution plot. 1. Each event must have only two possible outcomes. 2. Each event must be statistically independent of the others. Statistical independence means that the occurrence of one event does not have an effecton theprobabHity ofanyotherevent. 3. ThepcobebttttyoOtbe eutcome of anyevtetmuet be the tame from event toevent. In Che f .