Chapter 2 Data

Data are information in context The W’s help nail down the context The W’s help nail down the context Who - cases Who - cases What - variables What - variables Where Where When When Why – helps us determine what type of variable we have Why – helps us determine what type of variable we have hoW hoW You must know at least the who, what, and why to say anything useful about the data You must know at least the who, what, and why to say anything useful about the data

Two Types of Variables Categorical variable: identify a category for each case Categorical variable: identify a category for each case Quantitative variable: records measurements or amount of something; must have units Quantitative variable: records measurements or amount of something; must have units Remember to use the why to help you determine what type of variable you are looking at Remember to use the why to help you determine what type of variable you are looking at

Think Identify the W’s of data, recognize when the information is not given Identify the W’s of data, recognize when the information is not given Identify the cases and variables in a set of data Identify the cases and variables in a set of data Classify a variable as categorical or quantitative depending on its use Classify a variable as categorical or quantitative depending on its use Identify the units of quantitative variables Identify the units of quantitative variables

Show NONE NONE

Tell Describe a variable in terms of the W’s Describe a variable in terms of the W’s Be sure to mention information that was not provided Be sure to mention information that was not provided

What Can Go Wrong? Mislabeling variables: Mislabeling variables: Always think about the why before determining categorical vs quantitative variable Always think about the why before determining categorical vs quantitative variable numerical data is not always quantitative numerical data is not always quantitative Always be SKEPTICAL!!! Always be SKEPTICAL!!! Look at the context of the problem Look at the context of the problem People use bogus statistics to mislead you People use bogus statistics to mislead you