The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL STOR 155 Introductory Statistics Lecture 1 Overview 8 25 2009 Lecture 1 1 Registration Issues Contact Charlotte Rogers Hanes 321 962 2307 crogers email unc edu Fill out some paperwork with her to be put on the waiting list 8 25 2009 Lecture 1 2 My Strategy for Success Stay active involved in class Ask questions during class especially if you do not understand something Do not feel shy or stupid Answer questions to help other students if you can Keep pace with the lectures review daily do homework after each lecture to help understand the materials Make effective use of office hours Instructor and IA and open tutorial sessions Help you to answer questions about homework and lectures Private time vs public time 8 25 2009 Lecture 1 3 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 Statistics 8 25 2009 Lecture 1 4 What is Statistics Statistics the science of collecting organizing and interpreting data Population Inference about population using statistical tools Sample of data data information 8 25 2009 Lecture 1 5 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 8 25 2009 Lecture 1 6 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 8 25 2009 Lecture 1 7 SAT Scores After nine months all students were given the same standardized tests the verbal test and the mathematics test Student A 8 25 2009 Group Gender Strict F SATMath 670 SATVer 700 B C D Strict Liberal Liberal M F M 700 750 690 680 730 750 Lecture 1 8 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 8 25 2009 Lecture 1 9 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 8 25 2009 Lecture 1 10 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 all the students who are selected into the study a sample analogy of the parameter 8 25 2009 Lecture 1 11 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 unders 8 25 2009 Lecture 1 12 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 8 25 2009 Lecture 1 13 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 8 25 2009 Lecture 1 14
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