Statistics 224
Descriptive Statistics:
Numerical variables, distributions, and histograms
Alyssa Digilio
Questions about course logistics


Have you tried to buy the Freedman et al text
from “A room of one's own”? Or online?
Have you visited the course website?
http://www.stat.wisc.edu/~boehm/teaching/2014/stat224/syllabus.html

Homework 1 is posted –
http://www.stat.wisc.edu/~boehm/teaching/2014/stat224/hw1.pdf

Be sure to put your name and DISCUSSION (day
and time) on the BACK of your homework
Overview of Lecture
• Trends in data
• Categorizing data
• Categorical, continuous, or discrete
• Organizing data
• Histograms
• Making mathematically valid predictions about
data
World record times for the mile run
World record times for the mile run
Categorical, Continuous, and Discrete
Variables
• Categorical Variables
• “Categories”
• Ex: Do you eat breakfast?
• Continuous Variables
• A variable that can take on any value
• Ex: time
• Discrete Variable
• A variable that is numerical, but only can take
certain values
• Ex: How many times have you eaten today?
Categorical, continuous, and discrete
variables

Are the following take categorical, continuous,
or discrete values?
- Sex
- Age
- Number of siblings
- Height
- Income
- Spouse height
Histograms
•A graph used to organize
data
•Contains bins along the X
axis (typically intervals)
•Contains either a count or
a frequency along the Y
axis
•Used to show a
distribution
•Shows important features
such as skewness, mean,
and range of data
How much soda do people drink (per
day)?


Is a single number the best response? Why?
With a partner, sketch (on graph paper) a
distribution of (non-diet) soda consumption by
persons in the USA
Daily soda consumption
Daily soda consumption
Handedness Scores

Answer questions (Left or Right) on your index
card:
1.
Writing
2.
Drawing
3.
Throwing
4.
Scissors
5.
Toothbrush
6.
Knife (without fork)
7.
Spoon
8.
Broom (upper hand)
9.
Match striking (which hand holds match)
10.
Match striking (which hand holds lid)
RIGHT – LEFT = ?
RIGHT + LEFT = ?
(RIGHT – LEFT) / (RIGHT + LEFT) = ?
Handedness Scores

With a partner, draw (on graph paper) a guess
of the histogram of handedness scores
Handedness Scores: Sample guess
Handedness Scores (Real data)
Who opposed the Vietnam War?
Who opposed the Vietnam War?
Review of Lecture
• Trends in data can continue for short periods of
time, but may not hold over long periods
• Differences between types of variables
• How to read and construct a histogram
• How to use mathematical reasoning to make
educated guesses
References
Teaching Statistics: A bag of tricks. Gelman &
Nolan, 2002.