The definition of statistics How to distinguish between a population and a sample and between a parameter and a statistic How to distinguish between descriptive statistics and inferential statistics 1.1 An Overview of Statistics

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

Statistics Statistics is the science of collecting, organizing, analyzing, and interpreting data in order to make decisions.

Population A population is the collection of all outcomes, responses, measurements, or counts that are of interest.

Sample A sample is a subset, or part, of a population.

Try it yourself 1 Identifying Data Sets The U.S. Department of Energy conducts weekly surveys of approximately 900 gasoline stations to determine the average price per gallon of regular gasoline. On January 11, 2010, the average price was $2.75 per gallon. Identify the population and the sample. Describe the sample data set. (Source: Energy Information Administration) The population consists of the prices per gallon of regular gasoline at all gasoline stations in the United States. The sample consists of the prices per gallon of regular gasoline at the 900 surveyed stations. The data set consists of the 900 prices.

Parameter A parameter is a numerical description of a population characteristic.

Statistic A statistic is a numerical description of a sample characteristic.

Try it yourself 2 Distinguishing Between a Parameter and a Statistic In 2009, Major League Baseball teams spent a total of $2,655,395,194 on players’ salaries. Does this numerical value describe a population parameter or a sample statistic? (Source: USA Today) Because the $2,655,395,194 is based on all players in MLB, it is a population parameter.

Descriptive statistics Descriptive statistics is the branch of statistics that involves the organization, summarization, and display of data.

Inferential statistics Inferential statistics is the branch of statistics that involves using a sample to draw conclusions about a population. A basic tool in the study of inferential statistics is probability.

Try it yourself 3 Descriptive and Inferential Statistics A survey conducted among 1017 men and women by Opinion Research Corporation International found that 76% of women and 60% of men had a physical examination within the previous year. (Source: Men’s Health) Descriptive statistics involve the statement “76% of women and 60% of men had a physical examination within the previous year.” An inference drawn from the study is that a higher percentage of women had a physical examination within the previous year.