1. 1.2 Displaying Quantitative Data with graphs

2. Homework Questions?
Remember, I will give you points for completion, not accuracy

3. Now on to New Stuff

4. Now on to New Stuff How to describe:
Shape: how many peaks? Is one tail longer than the other (skewed)?
Center: where is the center point (or the median)?
Spread: minimum and maximum
Outliers: Are there any outliers?
SOCS

5. Shape
Symmetric
Skewed (to the right)

6. Center
Where is the center? (roughly)

7. Center
Where is the center? (roughly)
Roughly 7.5 pounds

8. Outliers
For now, we will assess whether something is an outlier visually
Does it look like there are any outliers?
Later, we will learn a rule for calculating it

9. Spread
The easiest way to describe the spread is simply to state the minimum value and the maximum value

10. An Example Describe the distribution
The distribution is single- peaked and skewed to the right, with probable outliers at 55, 38, and two possible outliers at 29. The center is roughly 7 electoral votes, with a minimum of 3 and a maximum of 55.

11. You try
Describe the distribution

12. You try Describe the distribution
The distribution is single- peaked and skewed to the left. There do not appear to be any outliers. The center of the distribution is around 73, with a minimum of about 46 and a maximum of about 83.

13. Stemplots I do not like them I do not find them helpful
But you’re expected to know what they are
Does anyone know what a stemplot is?

14. Stemplots
Let’s say that the class gets the following test grades: 42, 67, 73, 78, 82, 84, 86, 91, 91, 94, 99
The Stemplot would look like

15. Stemplots
You can also use a stemplot to compare two different datasets

16. Histograms The most common graph of a quantitative variable
Also, in my opinion, the most useful
Similar to a dotplot, but for larger datasets

17. Histograms
Notice that this is telling us the same information as a dotplot
Just larger counts
Looks a bit cleaner to some people

18. Histograms However, there are problems with histograms
Our eyes respond to the area of the bars
Can be confused with a bar graph
Bar graph is for categorical variables
Other problems (see pages )

19. You try Make a histogram for the following data:
Average first serve speed for 21 professional tennis players:
124.5, 122.1, 120.3, 119.7, 118.7, 116.5, 115.6, 114.5, 114, 113.9, 113.7, 112.6, 112.4, 112.3, 112.2, 110.5, , 108.3, 107.3, 103.1, 101.9

20. HW Time