COMM 250 Agenda - Week 12.ppt

Statistics Why Study Statistics ? Integral to the “Scientific Method” Seeing the Forest Amid the Trees Describing (Sports Statistics) Inferring (Correlates of Cancer) Predicting (Science, Business) To Pursue an ‘Objective’ View Statistics Descriptive Statistics: a way to summarize data Inferential Statistics: strategies for estimating population characteristics from data gathered on a sample Descriptive Statistics Measures of Central Tendency Used to describe similarities among scores What number best describes the entire distribution? Measures of Dispersion Used to describe differences among scores How much do scores vary? Inferential Statistics Used For - Estimation To Extrapolate from a Sample to a Population Significance Testing To Determine the Importance of Observed Differences; e.g., Between Groups or Variables Using Inferential Statistics for Estimation Purpose To Estimate (“Extrapolate”) from a Sample (Statistic) to a Population (Parameter) Reason Why It Saves Time and Money (Don’t Need to Survey/Measure the Entire Population) A Statistic Measure of a Sample (E.g., Comm250) on Some Variable E.g., Average (Mean) Height of Comm250 Students A Parameter A Characteristic of a Population (E.g., Virginia) E.g., Average (Mean) Height of Residents of VA Inferential Statistics Note: When Statistics are Used for Estimation, this is the “Heart” of Using Statistics to Infer - Statistic Measure of a Sample (E.g., HSers taking SAT in ‘02) on Some Variable E.g., Average (Mean) SAT score in 2002 E.g., Average (Mean) SAT score Among GMU Freshmen Parameter A Characteristic of a Population (E.g., All HSers Who Have Taken the SAT) E.g., Average (Mean) SAT Across ALL HSers (50 years?) Parametric Non-Parametric Parametric Statistics Stats Used to Establish Attributes of a Population Based on Attributes of a Sample Non-Parametric Statistics Stats Used ONLY to Describe The Attributes of a Sample No Generalization Back to Its Population is Attempted Inferential Statis