Definition of Statistics Statistics is the science of: - collecting - organizing - analyzing - interpreting data in order to make decisions.

Definition of Data Data consist of information coming from observations, counts, measurements, or responses.

Data Sets Population: all outcomes, responses, measurements, or counts Sample: a subset, or part, of a population

Example What is the population? What is the sample? A survey of 1000 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 What is the population? What is the sample? A survey of 1000 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 What is the sample? 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.

Parameter versus Statistic Parameter: a numerical description of a population characteristic Statistic: a numerical description of a sample characteristic

Parameter versus Statistic (examples) The 2009 payroll of the Philadelphia Phillies was $113,004,046. Fifty percent of a sample of 1508 US adults say they oppose drilling for oil in the Arctic Wildlife Refuge. In a recent study of math majors at a university, 10 students were minoring in physics. In a survey of 752 adults 42% think there should be a law that prohibits people from talking on cell phones in public places.

Descriptive versus Inferential Statistics Descriptive: branch of statistics that organizes and displays the data (describe) Inferential: branch of statistics that involves using a sample to draw a conclusion about a population (infer)

Example A tire manufacturer wants to estimate the average life of a new type of steel belted radial tire. descriptive study? inferential study?

Will the manufacturer look at all tires? 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!) of 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)