1. Probability and Sampling Distributions Probability Enquiry about chance Probability of winning a lottery based on buying a single ticket Probability of precipitation Probability of winning a hockey game to assess the likelihood of an event occurring.

2. Definitions for Probability Pp Parameter –describes a population Value not usually known Ss Statistic –computed from sample data Estimates unknown parameters Computed to estimate unknown parameters Mean, standard deviation, variability, etc. Notations Population mean – μ Sample mean - varies from one sample to another is an estimate of μ.

3. Probability Example: State whether each boldface number is a parameter or a statistic. A telemarketing firm in Los Angeles uses a device that dial residential telephone numbers in the city at random. Of the first 100 numbers dialed, 48% are unlisted. This is not surprising because 52% of all Los Angeles residential phones are unlisted. A researcher carries out a randomized comparative experiment with young rats to investigate the effects of a toxic compound in food. She feeds the control group a normal diet. The experimental group receives a diet with 2,500 parts per million of the toxic material. After 8 weeks the mean weight gain is 335 grams for the control group and 289 grams for the experimental group.