Chapter 2 Data In God We Trust all others bring data Unknown Chapter02 Presentation 1213 Copyright 2009 Pearson Education Inc 1 A Simple Survey Gender Number of siblings Number of countries ever visited Height Favorite coffee flavor at Starbucks Shoe size How could there be problems with responses to this survey Chapter02 Presentation 1213 Copyright 2009 Pearson Education Inc 2 Class Activity In groups of 2 or 3 discuss possible problems one might have with getting accurate answers to the questions outlined on the previous page Be prepared to discuss what you and your teammate discussed with the class Chapter02 Presentation 1213 Copyright 2009 Pearson Education Inc 3 Real Data Can Be Messy Different units of measure Ambiguous questions lead to ambiguous data Non response how will we handle Seemingly ridiculous responses how will we handle An important first step in getting meaningful data is carefully planning the data collection activity AND clearly defining the questions Chapter02 Presentation 1213 Copyright 2009 Pearson Education Inc 4 What Are Data Data can be numbers record names or other labels Not all data represented by numbers are numerical data e g 1 male 2 female Data are useless without their context Chapter02 Presentation 1213 Copyright 2009 Pearson Education Inc 5 Raw data What does this data tell us What does it mean Chapter02 Presentation 1213 Copyright 2009 Pearson Education Inc 6 Data in a context When the data are organized given labels and put into a context the data gain meaning Chapter02 Presentation 1213 Copyright 2009 Pearson Education Inc 7 The W s To provide context we need the W s Who What and in what units When Where Why if possible and How of the data Note the answers to who and what are essential Chapter02 Presentation 1213 Copyright 2009 Pearson Education Inc 8 2 Types of Variables A categorical or qualitative variable is one whose possible values are given by short descriptors Sex male female eye color blue brown favorite food birth state flight status zip codes Can encode as numbers e g female 1 male 2 A special kind of categorical variable is ordinal data e g data where the order is perceived to have worth but no units like Rate your professor on a scale of 1 to 5 or ranks in the military Chapter02 Presentation 1213 Copyright 2009 Pearson Education Inc 9 2 Types of Variables Cont A quantitative variable is one whose possible values must be numbers usually with units Income height inches weight pounds Ratio of left thumb length to right thumb length unitless Common business analytics quantitative variables are profit net increase tax rate days in inventory price Chapter02 Presentation 1213 Copyright 2009 Pearson Education Inc 10 Counts Statisticians often count things Counts can be categorical or quantitative Categorical Natural summary of categorical data is the count of each type Chapter02 Presentation 1213 Copyright 2009 Pearson Education Inc 11 Counts Cont Quantitative Number of CDs in a collection Number of classes taken this semester Number of items returned to seller Number of Chapter02 Presentation 1213 Copyright 2009 Pearson Education Inc 12 2 Types of Variables Cont Why do we differentiate between the two types Chapter02 Presentation 1213 Copyright 2009 Pearson Education Inc 13 Identifying Identifiers Identifier variables are categorical variables with exactly one individual in each category and can look like quantitative variable Examples Social Security Number ISBN FedEx Tracking Number Should these variables be summarized graphically or numerically What is the purpose of identifier variables Chapter02 Presentation 1213 Copyright 2009 Pearson Education Inc 14 Class Activity Answer the questions on the next two pages on your own After you have finished compare your answers with your teammate s If you have any differences in your answers discuss why you answered the way you did and try to come to a common answer Be prepared to discuss any differences you had with the class Chapter02 Presentation 1213 Copyright 2009 Pearson Education Inc 15 Types of Data Exercises What type of data are these variables Chapter02 Presentation 1213 Copyright 2009 Pearson Education Inc 16 Types of Data Exercises What type of data are these variables Chapter02 Presentation 1213 Gender Number of siblings Number of countries ever visited Height Favorite Starbucks flavor Shoe size Copyright 2009 Pearson Education Inc 17 Chapter Example pay at pump of transaction type of gallons number gas 9853 premium 22 y 9211 diesel 26 y 8875 regular 19 y 8824 regular 21 y 8313 regular 14 y 7699 premium 22 n 7645 diesel 45 y 3145 diesel 38 y 2588 regular 17 n 2499 regular 22 n 2325 premium 15 y 2291 diesel 22 y 2078 regular 14 y 1843 regular 35 y 2103 regular 25 n Chapter02 Presentation 1213 inside food sale n n y y y n y n y n n n y n y Copyright 2009 Pearson Education Inc type of payment Visa Am Exp Visa Visa MasterCard cash Am Exp Am Exp Visa cash MasterCard MasterCard Visa Visa cash Gas purchase in dollars 85 58 110 5 70 11 77 49 51 66 85 8 191 25 161 5 62 73 81 18 58 35 92 4 51 66 129 15 92 25 Day of week Mon Tues Tues Fri Wed Wed Sat Sat Sun Sat Fri Mon Thur Thur Sat 18
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