www.realeyes.it The f ollowing slides show how many participants are needed to get a reliable visual analysis of a web page

1 Large improvements in data quality

Large improvements in data quality 2

Large improvements in data quality 3

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Large improvements in data quality 8

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Large improvements in data quality 15

Moderate improvements in data quality 17

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Moderate improvements in data quality 22

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Moderate improvements in data quality 30

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Small improvements in data quality 35

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Small improvements in data quality 53

Some claim 8 people are enough to analyze visual attention. Following slides show random sets of 8 people from the same study shown on previous slides.

8 people Sample A

8 people Sample B

8 people Sample C

8 people Sample D

8 people Sample E

Heatmaps of random 8 people out of all 53 participants were very different. It means sample of 8 can give a very misleading picture of true visual attention.

Others claim 15 people are enough for visual analysis. How about that?

15 people Sample A

15 people Sample B

15 people Sample C

15 people Sample D

Variation is still too large for samples of 15 people. What about samples of 30?

30 people Sample A

30 people Sample B

30 people Sample C

CONCLUSION Reliable visual analysis demands samples larger than 30 people