The order of categories on the x axis is arbitrary, and the columns usually don't touch. Sales of animals at Scannell's Pet Shop. The order of categories on the x axis matters, and the columns usually touch. The scale on the x axis matters, and it is OK to draw lines between points if there is some reason to suppose that they represent data sampled from a continuum. L egend .
Motion detection varies with strength of motion signal.
The graph shows the percentage of correct responses in a motion detection task in which dots drift either left or right. Data are from 12 subjects who appear to fall into 3 groups. An old trick in advertising and politics is to fiddle with the scale on the axes to make changes or trends look bigger or smaller. Always check the scale on the axes when you are looking at or drawing graphs. Two graphs of exactly the same data.