Grid Lines and Tick Marks
· Tick marks are used to identify the type of scale, not to identify each data point. They should be long enough to be visible but not obtrusive.
· Tick marks on a linear scale should be the same length.
· Don’t label every tick mark, or the axis will look too cluttered. Number at
conventional intervals, e.g., 0, 2, 4, 6, 8,etc.
· Tick marks at the beginning of each logarithmic cycle should be longer than the others.Only tick marks at the beginning of cycles in logarithmic cycles should be numbered.
· Each axis should end at a tick mark.
· Tick marks can point in or out, but they should not cross the axis. Tick marks that point in direct the eye toward the data. Tick marks that point out keep the face of the graph clear and are particularly useful when data fall on the axis.