Chapter 1 Exploring Data Guided Notes

1.0 Data Analysis: Making Sense of Data Pages 2-7 Objectives SWBAT: 1)Identify the individuals and variables in a set of data. 2)Classify variables as categorical or quantitative.

What’s the difference between categorical and quantitative variables? A variable is any characteristic of an individual. A quantitative variable takes numerical values for which it makes sense to find an average. – Examples would include height, weight, speed, age, number of oranges in a bowl, number of stolen bases, etc... A categorical variable places an individual into one of several categories or groups. (think qualitative) – Examples would include gender, blood type, ethnicity, outcome of a plate appearance in baseball, etc…

Do we ever use numbers to describe the values of a categorical variable? Do we ever divide the distribution of a quantitative variable into categories? A word of caution: not every variable that takes number values is quantitative. – Example: zip codes. Zip codes are numbers, but they place individuals into categories (based on locations). – Another example would be social security number. You could just as easily use letters instead of numbers to represent someone’s identity. – A third example is AP scores. Students are categorized by scoring a 1, 2, 3, 4, or 5. Often, variables like age and weight are divided into categories and treated as a categorical variable. – An example would be age categories to classify people, such as 0-9, 10-19, etc…

What is a distribution? A variable generally takes on many different values. In data analysis, we are interested in how often a variable takes on each value. A distribution of a variable tells us what values the variable takes and how often it takes these values. – Note: the values can be words or numbers. Variable of Interest: MPG Variable of Interest: MPG Dotplot of MPG Distribution Example

Example: US Census Data, 10 randomly selected US residents a)Who are the individuals in this data set? 10 randomly selected US residents who participated in the 2000 US census b) What variables are measured? 1) state; categorical 2) number of family members; quantitative; units-ppl 3) age; quantitative; units- years 4) gender; categorical5) marital status; categorical 6) total income; quantitative; units: dollars 7) travel time to work; quantitative; units: minutes

c) Describe the individual in the first row. The individual lives in Kentucky, has 2 members in her family, is 61 yeas old, is female, is married, makes $21,000 a year, and travels 20 minutes to work.