Lecture_1 - Exploring Data with Graphs and Numerical...

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1 Exploring Data with Graphs and Numerical Summaries What Are the Types of Data?
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2 Learning Objectives 1. Know the definition of variable 2. Know the definition and key features of a categorical versus a quantitative variable 3. Know the definition of a discrete versus a continuous quantitative variable 4. Know the definition of frequency, proportion (relative frequencies), and percentages 5. Create Frequency Tables
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3 Learning Objective 1: Variable A variable is any characteristic that is recorded for the subjects in a study Examples: Marital status, Height, Weight, IQ A variable can be classified as either Categorical (or Qualitative), or Quantitative (Discrete, Continuous)
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4 Learning Objective 2: Categorical Variable A variable can be classified as categorical if each observation belongs to one of a set of categories. Examples: Gender (Male or Female) Religious Affiliation (Catholic, Jewish, …) Type of residence (Apt, Condo, …) Belief in Life After Death (Yes or No)
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5 Learning Objective 2: Quantitative Variable A variable is called quantitative if observations on it take numerical values that represent different magnitudes of the variable Examples: Age Number of siblings Annual Income
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6 Learning Objective 2: Main Features of Quantitative and Categorical Variables For Quantitative variables: key features are the center and spread (variability) For Categorical variables: a key feature is the percentage of observations in each of the categories
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7 Learning Objective 3: Discrete Quantitative Variable A quantitative variable is discrete if its possible values form a set of separate numbers, such as 0,1,2,3,…. Discrete variables have a finite number of possible values Examples: Number of pets in a household Number of children in a family Number of foreign languages spoken by an individual
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8 Learning Objective 3: Continuous Quantitative Variable A quantitative variable is continuous if its possible values form an interval Continuous variables have an infinite number of possible values Examples: Height/Weight Age Blood pressure
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9 How do you decide if a variable is categorical or quantitative? Ask: What are the n individuals/units in the sample (of size “ n ”)? What is being recorded about those n individuals/units? Is that a number ( quantitative) or a statement ( categorical)? Individuals in sample DIAGNOSIS AGE AT DEATH Patient A Heart disease 56 Patient B Stroke 70 Patient C Stroke 75 Patient D Lung cancer 60 Patient E Heart disease 80 Patient F Accident 73 Quantitative Each individual is attributed a numerical value Categorical Each individual is assigned to one of several categories
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10 Class Problem #1 Identify the variable type as either categorical or quantitative 1.
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Lecture_1 - Exploring Data with Graphs and Numerical...

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