What is the effect of checking the 'include zero on y-axis' option in trend graphs?

Checking the 'include zero on y-axis' option in trend graphs ensures that the graph starts plotting from zero on the y-axis. This is important for accurately portraying the scale of the data being presented. When the y-axis begins at zero, it provides a true visual representation of the data, allowing viewers to see the full extent of the variation in values. This can often highlight trends more clearly, as small differences in data values can appear exaggerated if the graph does not start at zero.

In contrast, starting the y-axis at a different value can misrepresent the significance of the data by making it look like there are larger changes or trends than actually exist. Therefore, enabling this option helps maintain the integrity of the visual data analysis.