Transcript chap1 sec1P
Definition of Data Data consist of information coming from observations, counts, measurements, or responses. Definition of Statistics Statistics is the science of: - collecting - organizing - analyzing - interpreting data in order to make decisions. Data Sets Population: all outcomes, responses, measurements, or counts Sample: a subset, or part, of a population Example A survey of 10000 adults found that 59% think buying a home is the best investment a family can make. What is the population? What is the sample? Example A survey of 10000 adults found that 59% think buying a home is the best investment a family can make. What is the population? The set of responses of all adults in U.S. What is the sample? Example A survey of 1000 adults found that 59% think buying a home is the best investment a family can make. What is the sample? The set of the responses of the 1000 adult surveyed. Example A tire manufacturer wants to estimate the average life of a new type of steel belted radial tire. descriptive study? inferential study? A tire manufacturer wants to estimate the average life of a new type of steel belted radial tire. Will the manufacturer look at all tires? Will the manufacturer take a sample of tires, examine the sample, and then conclude something about all tires? It is impractical to look at all/every tire. So one will take a reasonable and unbiased sample of the tires and examine the average age. From this sample average one can infer something about the age of all tires (the population). Thus an inferential study Example A sports writer plans to list the winning times for all the swimming events in the 2012 Olympics. descriptive study? Inferential study? A sports writer plans to list the winning times for all the swimming events in the 2012 Olympics. The writer wants to simply organize the data and compile a list (describe!) the medal winners of the Olympics descriptive study Descriptive versus Inferential A survey conducted among 1017 men and women found that 76% of women and 60% of men had a physical examination with the previous year. Inferential? Descriptive? A survey conducted among 1017 men and women found that 76% of women and 60% of men had a physical examination with the previous year. Inferential? Descriptive? Both! 76% women, 60% men Descriptive (simply describes the data sample which was collected) More women than men will have physical exams during the year Inferential (use the data sample to say something about the population)