1.1 An Overview of Statistics

The definition of statisticsHow to distinguish between a population and a sample and between a parameter and a statisticHow to distinguish between descriptive statistics and inferential statistics1.1 An Overview of StatisticsData:Data consist of information coming from observations, counts, measurements, or responses.StatisticsStatistics is the science of collecting, organizing, analyzing, and interpreting data in order to make decisions.PopulationA population is the collection of all outcomes, responses, measurements, or counts that are of interest.SampleA sample is a subset, or part, of a population.Try it yourself 1Identifying Data SetsThe 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.ParameterA parameter is a numerical description of a population characteristic.StatisticA statistic is a numerical description of a sample characteristic.Try it yourself 2Distinguishing Between a Parameter and a StatisticIn 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 statisticsDescriptive statistics is the branch of statistics that involves the organization, summarization, and display of data.Inferential statisticsInferential 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 3Descriptive and Inferential StatisticsA 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: Mens 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.