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Statistics are Tools! Statistics – techniques for organizing, summarizing, and interpreting data Which “tool” you choose depends on: What you want to know What type of data you have What kind of research design you used 1
Statistics and Research Statistics are used to analyze the data collected in a research study 2
Descriptive Statistics Techniques to organize, display, and describe data using tables, graphs, and summary measures. Number Letter % of Grade Grade Class 90s A 16 80s B 44 70s C 28 60s D 12 100 3
Inferential Statistics Techniques that enable us to use information gathered from a sample to make decisions, inferences, or predictions about a population. Allows statements that go beyond the current data or information. 4
Examples of Inferential Statistics TV networks monitor the popularity of their programs by hiring Nielsen and other organizations to sample the preferences of TV viewers. The accounting department of a large firm will select a sample of the invoices to check for accuracy for all the invoices of the company. Pre-election polling techniques used to predict election results “Based on our sample of 10,000 drivers across the U.S., we estimate that between 34% to 40% of all U.S. drivers are driving on underinflated tires.” 5
Populations and Parameters Suppose a statistician wanted to know: Average gpa all students accepted to OLLU Gross sales at Church’s Fried Chicken stores this year in San Antonio Average customer satisfaction rating for all Target stores in San Antonio Population is all elements (can be people or things) whose characteristics are being studied. Also called the “target population.” A value (average, total, etc.) that is calculated from the entire population is called a parameter. 6
Samples and Statistics Recall that the statistician wants to know the average customer satisfaction rating for all Target stores in San Antonio. A survey is given to every 100th customer at 5 randomly selected Target stores in S.A. during a three day period A sample is a subset of the population that is selected for study. A value that is calculated from a sample is called a statistic. 7