Intro to Statistics and Data Chapter 1 Chapter 2

What is Statistics? Statistics is the science of learning from data, and of measuring, controlling, and communicating uncertainty In a word: variation

Think, Show, Tell Think first. Know where you are headed and why. Show your work. The mechanics of the calculation are important but can not exist on there own. Tell your conclusion in the context of the problem

What are these? 16 37 46 25 33 45 24 42 19 40 5 26 34 28 49 73

Barry Bonds HRs by year 1986 16 1994 37 2002 46 1987 25 1995 33 2003 45 1988 24 1996 42 2004 1989 19 1997 40 2005 5 1990 1998 2006 26 1991 1999 34 2007 28 1992 2000 49 1993 2001 73

Data Information in context Context: Who What (and in what units) Why (if possible) Where When How By Whom

The W’s Who?-- The cases (or individuals) about which (or whom) we gather information MLB Seasons from 1986 to 2007 What? – Variables are characteristics recorded about each case Barry Bonds’ HRs (HRs) Why? – The reasons for gathering the data can influence our analysis, can help determine which type of variable

The W’s cont. When and where? – Help provide additional context for the data How? – The methodology for gathering the data can determine whether you have useful information or pure crap

More about What Variables come in two types A categorical (or qualitative) variable names categories and answers questions about how cases fall into those categories. (e.g., sex, race, ethnicity) A quantitative variable is a measured variable (with units) that answers questions about the quantity of what is being measured. (e.g. income ($), height (inches), weight (pounds)) !!!Always include units!!!

What can go wrong? Don’t label a variable as categorical or quantitative without thinking about the question you want it to answer. Just because your variable’s values are numbers, don’t assume that it’s quantitative. Always be skeptical—don’t take data for granted.