Chapter 17 STATS.docx

Chapter 17 Thinking about ChancesThe idea of probability Favouritism in choosing subjects for a sample survey or allotting patients to treatment and placebo groups in a medical experiment is as undesirable as it is in awarding first possession of the ball in football Chance behaviour is unpredictable in the short run but has a regular and predictable pattern in the long run Probability describes what happens in very many trails and we must actually observe many coin tosses or many babies to pin down a probability We call a phenomenon random if individual outcomes are uncertain but there is nonetheless a regular distribution of outcomes in a large number of repetitionsThe probability of any outcome of a random phenomenon is a number between 0 and 1 that describes the proportion of times the outcome would occur in a very long series of repetitions An out come with probability 0 never occurs An outcome with probability 1 happens one very repetitionAn outcome