Final answer:
Using percentages rather than counts in a histogram for comparing weight classes across different years or countries standardizes the data for equitable comparisons. Bar graphs represent these percentages to effectively show the distribution and comparisons, even when the percentages do not add up to exactly 100 percent, which is a limitation of pie charts.
Step-by-step explanation:
When comparing data across different years or countries, using percentages in a histogram is preferable to using counts because it standardizes the representation, allowing for more equitable comparisons. For instance, using raw counts can be misleading when comparing two countries with vastly different population sizes, as the larger country may naturally have more people in each weight class simply due to its larger population. By using percentages, each country's data is scaled relative to its own total population, thereby providing a straightforward comparison of the distribution of weight classes across countries.
A bar graph is a versatile tool that can compare a variety of quantitative categories such as size, quantity, rates, distances, and percentages. In a bar graph, the length of the bar represents the number or percent of individuals in each category, which can be vertical or horizontal. This format is particularly useful when we want to compare categories or show changes over time. Furthermore, a bar graph is appropriate when percentages add to more (or less) than 100 percent, a scenario where pie charts are not applicable because they are designed to represent parts of a whole that must add up to 100 percent.