1. Bell Ringer What percent of females have brown eyes?
Blue
Brown
Green/Hazel
Total
Males 6 20 32
Females 4 16 12 10 36 18 64
What percent of females have brown eyes?
What percent of brown-eyed students are female?
What percent of students are brown-eyed females?
What’s the distribution of eye color? (Percent of each color for all participants)
What’s the conditional distribution of eye color for males?
Compare the percent of female among blue-eyed students to the percent of all students who are female.

2. Displaying and Summarizing Quantitative Data
Chapter 4
Displaying and Summarizing Quantitative Data

3. Dealing with lots of numbers…
Summarizing the data will help us when we look at large sets of quantitative data.
Without summaries of the data, it’s hard to grasp what the data tell us.
The best thing to do is to make a picture!
We can’t use bar charts or pie charts for quantitative data, since those displays are for categorical variables.

4. Types of Displays for Quantitative Data
Histogram
Stem-and-Leaf Display
Dot Plot
Boxplot (box and whisker)

5. On December 26, 2004 an earthquake with a magnitude of 9
On December 26, 2004 an earthquake with a magnitude of 9.0 on the Richter scale set into place a disastrous tsunami off the west coast of Sumatra. It killed an estimated 297,248 people.
CBS News Coverage
RIFT Numerical Model Animation of the Dec. 26, 2004 Indian Ocean Tsunami

6. (We’ll come back to this)
Histograms
Displaying the Distribution of Earthquake Magnitudes that Caused Tsunamis
(We’ll come back to this)

7. I’ve seen histograms before…
… but how do I make one?

8. First, divide the data into equally spaced intervals.
These intervals (or bins) have a width of 0.2
The magnitudes range from 3.0 to 9.0

9. Next, count how many values fall into each interval (or bin) and that will determine the height if the bars.
Approximately 100 of the magnitudes were between 6.6 and 6.8 on the Richter scale.

10. Which bin contains the most values?
A gap on a histogram indicates that no values were recorded in that interval. In this histogram, there is a gap from 3.8 to 5.0
Which bin contains the most values?
7.0 to 7.2

11. The following numbers represent the total numbers of points scored by both teams in each of the first 42 Super Bowl games.
Create a histogram using a bin width of 10.
Create a histogram using a bin width of 5.

12. A relative frequency histogram has the same shape distribution as a regular histogram but rather than displaying a count, it displays the percentage of the total number of cases in each bin.
Notice the vertical axis has changed from a count to a percent of all measured Earthquakes with a given magnitude.

13. Do the exercise on page 46, creating a histogram on a graphing calculator.

14. A stem-and-leaf display shows the individual values.
Histograms provide an easy-to-understand display of the distribution of a quantitative variable, but the individual values aren’t visible. 8 4 7 6 2 5
A stem-and-leaf display shows the individual values.
Pulse rates of 24 women at a health clinic.

15. Now, create a stem-and-leaf display using the Super Bowl data from the previous example.

16. A dotplot is very similar to a stem-and-leaf display, but it consists of dots instead of numbers.
This is a dotplot of Kentucky Derby winning times with each race as its own dot.
See how it’s done!

17. What is the difference between a bar chart and a histogram?
Write a few sentences to explain.

18. Today's Assignment:
Continue working on your newspaper article
(due Wednesday)