Effects of lines of progress and semilogarithmic charts on ratings of charted data.

The researchers asked people to look at behavior graphs. Some graphs had slanted progress lines drawn on them. Some used semilog paper. Some had both. The viewers then rated whether the data showed a real change.

The team measured how much the viewers agreed with each other. They also noted whether the viewers thought the change was big enough to matter.

When progress lines were added, viewers agreed more often. They also rated the same jump in data as more important.

Semilog charts gave an extra boost. The mix of both tools helped the most.

Deochand et al. (2015), Fuller et al. (2019), and Deochand (2017) each built on this idea. They turned the old hand-drawn lines into easy Excel steps. Now you can add locked, auto-updating phase lines in seconds.

Sunde et al. (2022) took the same goal—better agreement—and made a checklist for FA graphs. Their checklist hit 98% agreement, showing the idea still works when you move from progress lines to structured rules.

Friedling et al. (1979) had earlier tried a different graphic aid: a gray band that shows observer disagreement. Both studies chase the same end—helping viewers trust what they see—but use different visual tricks.

You want your team to see the same story in the data. Draw a progress line or use the free Excel tools from the follow-up papers. One quick line cuts arguments and makes change look real. Try it on tomorrow’s graph and watch staff nod faster.