1. Frequency Distributions
Frequency Distribution – Group Data into a set of k Ordered Classes
Class Limits – Largest and Smallest Values in the Class
Class Mark – Midpoint of the Class
Class Frequency – Number of Observations within the Class

2. Example:
Age Freq
30&Up 2 40
Guidelines:
All Classes Should be:
Of Equal Width
Mutually Exclusive
All-Inclusive
Method: = 16
Choose Number of Classes (Power of 2 Rule) n ≤ 2k = 32
26 = 64
Class Width Class Width > Range/k
Construct Frequency Distribution

3. Example: Injury Rate per Week per 1,000 Work-Hrs

4. Injury Rate Freq Rel Freq 1.8 – 2.3 3 2.4 – 2.9 9 3.0 – 3.5 20
1.8 –
2.4 –
3.0 –
3.6 –
4.2 –
4.8 – 52
Relative Frequency = Class Frequency/Number of Observations
Example: St Petersburg Burbank
Age Freq Rel Freq Freq Rel Freq
~ ~ ~ ~ ~
65&Up 90, ,
300, ,

5. Graphical Representations:
Histogram – Bar Chart of a Frequency Distribution

6. Frequency Polygon – Line Chart of a Frequency Distribution

7. Cumulative Frequency – Number of Observations Up to a Point
Injury Rate Cumulative Freq Relative Cum Freq
Less than 2.4
Less than 3.0
Less than 3.6
Less than 4.2
Less than 4.8
Less than 5.4
Injury Rate Freq Rel Freq
1.8 –
2.4 –
3.0 –
3.6 –
4.2 –
4.8 –

8. Ogive Curve – A Graph of the Relative Cumulative Frequency

9. Stem & Leaf Analysis Age data: 17 18 19 19 20 20 21 24 Stem | Leaf
1 | 7899
2 | 0014
Break Stem into 2 Parts:
Stem | Leaf
2* |
2. |
Break Stem into 5 Parts
Stem | Leaf
2* | 01
2T | 23
2F | 45
2S | 67
2. | 89
2 digit Leaves:
| 4 or 1 | 5

10. Stem & Leaf Analysis of Injury Rate Data
Cum Freq Stem | Leaf
| 8
* | |
(16) * | |
* | |
* | 3

11. MPG achieved with 100 cars
10 Classes

12. 5 Classes
5 Classes
20 Classes

13. Duration of Old Faithful

14. Mosaic Plot – Titanic Data