Pie chart vs. Bar chart figth

Experiment conducted on 22 university students divided into 2 groups (11 each). Each group was shown 1 pie chart and 1 bar chart showing election results. The students were asked to estimate the percentage won by each party (later rescaled to sum 100%).

The chart above summarizes the experiment's results:

• Every point is one error of estimate (by one student)
• Green circles are error of estimates based on a pie chart
• Blue squares are error of estimates based on a bar chart
• Horizontal lines connect estimates by one person, colored by the election
• Vertical lines show variance, the 2 extreme error of estimates in each groups are taken away
• Green lines are for error of estimates from pie chart, blue lines are for bar chart
• The values on x-axis are slightly randomly moved, so the overlapped points may be visible.

There is no clear evidence that any of the charts performs better, the results are slightly better for pie charts. But the sample is not big enough for better conclusions.

The actual file used for the experiment is here. The table below shows the experimental design:

	Election 1	Election 2
Group 1:
Group 2:

The real values were:
Election 1: 0.2910, 0.2499, 0.1804, 0.1793, 0.0994
Election 2: 0.3024, 0.2450, 0.1853, 0.1429, 0.1244