1.1 Overview of Statistics Statistics Mrs. Spitz Fall 2008

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

Definition: Data Data consist of information coming from observations, counts measurements or responses. The singular for data is datum.

Data Sets There are two types of data sets you will use when studying statistics: populations and samples. Population is the collection of ALL outcomes, responses, measurement or counts that are of interest. Sample: the subset of the population.

Ex. 1: Identifying Data Sets In a recent survey, 3002 American adults were asked if they read the news on the Internet at least once a week. Six hundred of the adults said yes. Identify the population and the sample. Describe the data set.

Ex. 1: Identifying Data Sets In a recent survey, 3002 American adults were asked if they read the news on the Internet at least once a week. Six hundred of the adults said yes. Identify the population and the sample. Describe the data set.

Ex. 1: Identifying Data Sets In a recent survey, 3002 American adults were asked if they read the news on the Internet at least once a week. Six hundred of the adults said yes. Identify the population and the sample. Describe the data set.

Ex. 1: Identifying Data Sets In a recent survey, 3002 American adults were asked if they read the news on the Internet at least once a week. Six hundred of the adults said yes. (population) – 600 (Given) 3002 – 600 = 2402.

Ex. 1: Identifying Data Sets The data set consists of 600 yes’s and 2402 no’s.

Try it yourself The US Dept of Energy conducts weekly surveys of 800 gasoline stations to determine the average price per gallon of regular gasoline. On July 10, 1998, the average price was $1.066 per gallon. Identify the population and the sample.

Try it yourself A. Identify the population B. Identify the sample. C. What does the data set consist of ?

Try it yourself A. Identify the population The populations consists of the prices per gallon\ of regular gasoline at all gas stations in the U.S.

B. Identify the sample. The sample consists of the prices per gallon of regular gasoline at the 800 surveyed locations.

Try it yourself C. What does the data set consist of ? The data set consists of the 800 prices.

So... Whether a data set is a population or a sample usually depends on the context of the real-life situation. For instance, in Ex. 1, the populations was the set of responses of all adult Americans. Depending on the purpose of the survey, the population could have been the set of responses of all adult Americans who live in California or who have telephones, or who read a particular newspaper.

Definitions PARAMETER: a numerical description of a population characteristic. STATISTIC: a numerical description of a sample characteristic.

Ex. 2: Distinguishing between a parameter and a statistic. Decide whether the numerical value describes a population parameter or sample statistic. Explain your reasoning. 1. A recent survey of a sample of MBA’s reported that the average starting salary for an MBA is less than $65,000l 2. Starting salaries for the 667 MBA graduates from the University of Chicago School of Business increased 8.5% from the previous year.

Ex. 2: Distinguishing between a parameter and a statistic. Decide whether the numerical value describes a population parameter or sample statistic. Explain your reasoning. 1. A recent survey of a sample of MBA’s reported that the average starting salary for an MBA is less than $65,000 Because of the numerical measure of $65,000 is based on a subset of the population (MBA’s), it is a sample statistic.

Ex. 2: Distinguishing between a parameter and a statistic. Decide whether the numerical value describes a population parameter or sample statistic. Explain your reasoning. 2. Starting salaries for the 667 MBA graduates from the University of Chicago School of Business increased 8.5% from the previous year. Because the numerical measure of 8.5% is based on all 667 graduates’ starting salaries, it is a population parameter.