Here's a chart that can save your life.
Here's my version (pretty much any such grouped column charts can be replaced by line charts):
(Chart purists: I like profile charts which means I like to connect categorical data with lines.)
Anyhow, this data supposedly came from an FDA study, which the FDA has apparently now disowned, according to this AOL News report. Rats were used in this study, and the rate at which they developed significant tumor or lesion was measured. The graph illustrated a clear trend that the higher the doses of Vitamin A, the faster the rats developed cancer; this correlation was intact whether they were exposed to high or low levels of UV rays.
Notice that I switched the primary categorical axis to Vitamin A doses rather than high/low UV because the study concerned Vitamin A primarily, and levels of UV secondarily.
Using the Trifecta Checkup, we can see that they have the right question, and the right data but a suboptimal chart. Also, the original chart fails the self-sufficiency test: no point in printing the data on top of the columns when there is a vertical scale.
How will this save your life?
Vitamin A is widely added to sunblocks -- not because they have any screening value -- but because they may slow aging of the skin. But the study found that Vitamin A actually partially nullifies the screening ability of sunblocks.
About half of the 500 most popular sunblocks sold in the U.S. contain Vitamin A and only 39 out of the 500 are deemed safe by the Environmental Working Group, which has compiled a database of these products. (There are several other potentially harmful ingredients.)
The FDA denied that such a study existed although the reporter as well as EWG have copies of it. If this study is authentic, the FDA knew about this perhaps ten years ago.
Reference: "Study: Many Sunscreens May Be Accelerating Cancer", Andrew Schneider, AOL News, May 24 2010.
PS. I should explain to my non-U.S. readers that the U.S. is celebrating Memorial Day, the beginning of summer, on Monday so lots of people are going to beaches and other vacations.