Chapter 1 Introduction
statistics
 the science of learning from data
data are numbers with a context must know your field
measurements from study are of little value without tools of statistics
individuals
 objects described by set of data (people, things…)
variable
 any characteristic of an individual
Why?
Why are we looking at this data?
Who?
Who are the individuals in the data set?
What?
What variables are in the data set?
categorical variable
 places an individual into one of several groups or categories
EX gender, race, ethnicity, hair color
quantitative variable
 takes numerical values for which arithmetic operations (adding,
averaging…) make sense
EX height, distance, cost, time, income
distribution
 tells us what values a variable takes and how often it takes those values
know what each variable is measuring
often the rate at which something occurs is a more meaningful measure than a count
EX in 2002:
27,102 passenger cars were involved in fatal accidents
3339 motorcycles were involved in fatal accidents
passenger cars had 21 fatal accidents per 100,000 vehicles
motorcycles had 67 fatal accidents per 100,000 motorcyles
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document1.1 Displaying Distributions with Graphs
exploratory data analysis
 examining data in order to describe their main features
examine each variable by itself, then study the relationship between variables
begin with graphs, then add numerical summaries
Graphs for categorical variables
distribution
 lists categories and gives either the count
or the percent
Distribution of highest level of education for people aged 2534
Education
Count (millions)
Percent
Less than HS
4.6
11.8
HS
11.6
30.6
Some college
7.4
19.5
Associate degree
3.3
8.8
Bachelor’s degree
This is the end of the preview.
Sign up
to
access the rest of the document.
 Spring '08
 ABDUS,S.
 Bar chart, horizontal axis

Click to edit the document details