Graphs can be used to effectively demonstrate the data you are describing. To ensure that the graphs are an accurate reflection of the information, the following guidelines should be followed.
- Axis labels should always start with "0".
- Describe whether the data are numbers or rates.
- If you are doing several graphs on the same subject, make sure the numerical scales are comparable.
- Data labels should be placed above the bars/points in the graph.
- Always include the source of the data.
- When using a term such as "teenagers," describe the age in the footnote (e.g. residents age 15-19 years of age).
- If using rates, describe the type and denominator (e.g. age-adjusted, age-specific, per 1,000, per 100,000, etc.)
To demonstrate the reason behind beginning the axis labels with "0", below are two possible outcomes for a chart of the age-adjusted death rate for motor vehicle injuries from 1994-1998 for Fayette County and Indiana:
The age-adjusted death rates are the same in both graphs. The graph on the left does not use a zero as the start of the axis. The results are exaggerated and do not accurately represent the data. The graph on the right is done correctly in terms of the axis beginning with zero.