One of my pet peeves is dates in charts that are ambiguous, but the problem can easily by avoided by choosing good date formats.

Probably the most common way to show values on a map is the "colored-region" or "choropleth" method. I'm not the first to notice, however, that this method presents some potentially serious perceptual risks.

I was recently invited to deliver a webinar as part of JMP's great Statistically Speaking series. The webinar consisted of a 35-minute talk entitled "How to choose a chart type (it's trickier than you think)," followed by about 25 minutes of Q&A from a very engaged (and large) audience. The recording is now available to view online.