How can changing the interval on a bar graph change the way it is interpreted?

Answer 1

Let's say you have 2 bars, one of which is 5 and one of which is 15 (units not important).

If you have the interval at 1 unit, then both bars would be relatively large. If you set the interval at 10 units, however, the bars suddenly seem much smaller. It's not because they ARE smaller, but because the interval makes them appear as such.

So if someone wanted to skew a statistic, such as "Number of deaths by cigarettes in 2009", they could set the interval at a high number to make it appear to be a smaller bar, which gives the impression that it's not that big of a deal. Conversely, if they wanted to skew a statistic the other way, such as "Units Produced in March", they could set the interval at a very low number which would make the bar appear very large, giving the effect of a large amount produced.