Vertical scale can greatly change the perceived difference between values on a histogram, bar graph, or really any type of graph. Suppose you have three values, 90, 95, and 100. If you show a normal histogram with a range of 0-120, and units of 10, the three values will appear quite similar. However, if you change the range of the graph to 80-110, the three values will appear to be much farther apart.