Descriptive statistics
Histograms
- Interpreting density histograms, uniform ranges vs. non-uniform ranges.
The vertical scale is in percent/unit range rather than frequency.
- y = 2.1 2.2 2.3 2.4 3.5 4.5 5.5 6.5
- For non-uniform ranges, to find the height, divide the percent by the length of
the interval.
- What happens when some of the data are close to the range boundaries?
- Draw a histogram for
2.1, 2.2, 2.3, 2.4, 2.1, 2.2, 2.3, 2.4, 3.5, 3.6, 4.4, 4.5, 5.5, 5.5, 6.5,
7.1, 7.2, 7.5
- When is it better to use non-uniform ranges?
- Drawing histograms
| Income level | Percent |
| $0 - $1,000 | 1 |
| $1,000 - $2,000 | 2 |
| $2,000 - $3,000 | 3 |
| $3,000 - $4,000 | 4 |
| $4,000 - $5,000 | 5 |
| $5,000 - $6,000 | 5 |
| $6,000 - $7,000 | 5 |
| $7,000 - $10,000 | 15 |
| $10,000 - $15,000 | 26 |
| $15,000 - $25,000 | 26 |
| $25,000 - $50,000 | 8 |
| $50,000 and over | 1 |
Draw histogram of education level completed in 1991.
The interval does not include the upper bound, for example 8-9 includes those
who finished 8th grade but not 9th, including those who started 9th.
| education level | Percent |
| 0 - 5 | 2 |
5 - 8 | 4 |
8 - 9 | 4 |
9 - 12 | 11 |
12 - 13 | 39 |
13 - 16 | 18 |
16 or more | 21 |