1/11/2011 Lecture 1 1 STOR 155 Introductory Statistics Lecture 1: Overview The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL1/11/2011 Lecture 1 2 Registration Issues • Contact Charlotte Rogers: Hanes 321, 962-2307, [email protected] • Fill out some paperwork with her to be put on the waiting list.1/11/2011 Lecture 1 3 Suggested Strategy for Success • Stay active/involved in class. • Ask questions during class (especially if you do not understand something). • Answer questions to help other students if you can. • Keep pace with the lectures, review daily, do homework after each lecture to digest the materials. • Make effective use of office hours (Instructor and IA) and open tutorial sessions (OTS) – Help you to answer questions about homework and lectures, e.g. Excel and stat.1/11/2011 Lecture 1 4 What is Statistics? • "Data! Data! Data!" he cried impatiently. "I can't make bricks without clay." ----Sherlock Holmes The Adventures of the Copper Beeches • "Data! Data! Data!" he yelled loudly. "I can't teach Statistics without Data." ----Instructor Introductory Statistics1/11/2011 Lecture 1 5 What is Statistics? • Statistics: the science of collecting, organizing, and interpreting data. • data = information Inference about population (using statistical tools) Population Sample of data1/11/2011 Lecture 1 6 How can Statistics help us? • claims that it contains 1000 chips. Is this true? • Among a group of randomly chosen people, how likely is it for two of them to have the same birthday? • What is the relationship between Income and Years of Education? • Design your own experiment, collect data, analyze data and draw conclusions.1/11/2011 Lecture 1 7 SAT Scores • Parents and teachers have been concerned about the trend of declining SAT scores and sought ways to halt the decline. • One question: the effect of classroom atmosphere (strict or liberal). • To answer the question, 50 students (24 males and 26 females) participated in a study on student performance, as measured by SAT scores at the end of the school year. • The students were divided into two groups of 25 each (12 males and 13 females), with Group 1 to study under a strict atmosphere while Group 2 under a very permissive atmosphere. • They were matched according to socio-economic background.1/11/2011 Lecture 1 8 SAT Scores • After nine months, all students were given the same standardized tests: the verbal test and the mathematics test. Student Group Gender SATMath SATVer A Strict F 670 700 B Strict M 700 680 C Liberal F 750 730 D Liberal M 690 750 … … … … …1/11/2011 Lecture 1 9 SAT Scores • This example involves data collection, data analysis, and statistical inference. – How? • Questions: – Does stricter classroom atmosphere increase the average score? – Why “matched according to socio-economic background”? – Why “12 males and 13 females per group”? – Is the group size 50 large enough to make a confident conclusion?1/11/2011 Lecture 1 10 Fundamental Concepts • Population: the entire group of individuals that we want information about. – Students (who are about to take SAT) • Sample: a part of the population that we actually examine in order to gather information. – those students selected into the study • Sample size: number of observations/individuals in a sample. – 50 • Statistical inference: to make an inference about a population based on the information contained in a sample. – Based on the data from the study, to infer whether a stricter classroom atmosphere increases SAT scores in general.1/11/2011 Lecture 1 11 Fundamental Concepts • A parameter is a value that describes the population. It’s fixed but unknown in practice. – the average SAT score of all the students, who are about to take SAT. • A statistic is a value that describes a sample. It’s known once a sample is obtained. – the average SAT score of those students selected to participate in the study. – a sample analogue of the parameter.1/11/2011 Lecture 1 12 Practice Exercise • Suppose you are interested in finding out the average SAT score of UNC unders, – The SAT scores of all UNC unders in STOR155 – The SAT scores of all UNC unders • Suppose you are interested in finding out the average SAT score of US unders, – The SAT scores of all UNC unders – The SAT scores of all US unders1/11/2011 Lecture 1 13 Take Home Message • Statistics is the science of data: – Collecting – Analyzing – Decision making = Information processing • Fundamental concepts: – Population, parameter, sample, statistic, sample size • You can do a LOT with statistics … what ?Take home message • Interested in population, but it’s too large to become known completely • Statisticians work on sample, which is a smaller and observable ``proxy’’ • There is uncertainty in this transition, hence errors are inevitable … • That’s why statistical methods are needed … 1/11/2011 Lecture 1
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