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Stats Starts Here • Statistics gets a bad rap, and • Statistics courses are not necessarily chosen as fun electives, but • Statistics can be fun! Learning to think clearly with data will open your eyes to seeing the world more clearly… Copyright © 2004 Pearson Education, Inc. Slide 1-1 What Is (Are?) Statistics? • Statistics (the discipline) is a way of reasoning, along with a collection of tools and methods, designed to help us understand the world. • Statistics (plural) are particular calculations made from data. • Data are values along with a context. Copyright © 2004 Pearson Education, Inc. Slide 1-2 What is Statistics Really About? • In a word, Statistics is about variation. • When we make measurements, there is variation out there that we cannot see, so all measurements are imperfect. • Statistics is thus a way for us to understand the real, imperfect world in which we live. Copyright © 2004 Pearson Education, Inc. Slide 1-3 Think, Show, Tell • There are three simple steps to doing Statistics right: think, show, and tell: – Think first. Know where you’re headed and why. It will save you a lot of work. – Show is what most people think Statistics is about. While the mechanics of calculating statistics and graphical displays are important, they are not the most important part of Statistics. – Tell what you’ve learned. Until you’ve explained your results so that someone else can understand your conclusions, the job is not done. Copyright © 2004 Pearson Education, Inc. Slide 1-4 Statistics – What do students find hard? • “Understood the material in class, but found it hard to do the homework.” • “Should be more like a math course, with everything laid out beforehand.” • “More problems in class should be like the HW and tests …” Copyright © 2004 Pearson Education, Inc. Slide 1-5 Easy Part /\ Hard Part • The easy part – Given the formula, turn the crank ... • The hard part – Putting it all together » Real world » Experience » Methods Copyright © 2004 Pearson Education, Inc. Slide 1-6 Example … • • • • • • • • Wed 6/22/2011 5:58 PM Dr. Robinson, • Wed 6/22/2011 6:15 PM • • Never mind I got it! I can’t figure out the problems of 9.1 numbers 17 and 19. How do I determine the lower and upper bounds? This is so frustrating Thank you ---------------------------------------------------------------------------------------------------------------- Copyright © 2004 Pearson Education, Inc. Slide 1-7 So What Do We Know? • Statistics can be (and is) fun! • Statistics gives us a way to work with the variability in the world around us. • We are embarking on an exciting journey of learning Statistics… Copyright © 2004 Pearson Education, Inc. Slide 1-8 WHAT IS STATISTICS? Statistics is a group of methods used to collect, analyze, present, and interpret data and to make decisions. 9 Descriptive Statistics consists of methods for organizing, displaying, and describing data by using tables, graphs, and summary measures. Inferential Statistics consists of methods that use sample results to help make decisions or predictions about a population. 10 A population consists of all elements – individuals, items, or objects – whose characteristics are being studied. A portion of the population selected for study is referred to as a sample. 11 A variable is a characteristic under study that assumes different values for different elements, units, subjects, individuals. 12 • Quantitative Variables – Discrete Variables – Continuous Variables • Qualitative/Categorical Variables 13 Variable Quantitative Discrete (e.g., number of houses, cars, accidents) Continuous (e.g., length, age, height, weight, time) Qualitative or categorical (e.g., make of a computer, hair color, gender) 14 From Where Does Data Come … ?? • • • • Published Source Designed Experiment Survey Observational Study 15 [Random] Sampling Techniques • • • • Simple Random Sampling Stratified Sampling Systematic Sampling Cluster Sampling 16 Uncertainty … Nonsampling Errors -- poor design, bias input errors, … Sampling Errors – using sample info [risk of inference] 17