Kids should use bar graphs when they are attempting to show how something changes over time or to compare items. Bar graphs work well when comparing items in categories that are related.
Bar graphs work well when plotting data that covers a number of days, weeks or years. This is especially true if the data that is being plotted shows significant changes during the specific time period. The graph has an x-axis that runs horizontally along the bottom of the graph and a y-axis that extends vertically. The x-axis of the graph is typically used to show the time period the graph spans or what is being measured, while the y-axis typically shows the amount of the item that is being measured.