When feedback is worthless

I just finished teaching another semester of Anatomy and Physiology which means students will soon be evaluating my course. Well, about 20% of my students will be evaluating my course. Why such little feedback?

About a year ago the University decided to switch from in-class paper evaluations to an online system. Online is always better, right? Wrong.

While going to an online system may decrease the work of a few administrators, it renders the whole evaluation worthless because so few students choose to respond to the optional online survey. The students who do respond likely either really liked or hated you. Talk about biased results! I wonder how much money is spent on this now useless form of feedback.

Take home message: don’t waste resources collecting data that is worthless upon arrival.

Your DNA is as elastic as nylon

In a paper published last year, scientists measured DNA’s elasticity and found it to be 83 newtons per meter, or about like nylon. Although DNA is not pulling a suburban like Travis Ortmayer in the above video (a hemp rope would have been much less elastic, see video), it does need to unzip and coil extensively. So if you plan on using string or rope to teach about DNA replication or histones, use nylon!

Export R plot to Illustrator or Inkscape

Have you ever exported an R plot as a PDF and tried to edit it further by importing the PDF into a vector graphics program like Adobe Illustrator or Inkscape? What typically happens is the points on the plot get converted into text of some sort, usually the letter “q”. To avoid this problem simply export your file as a postscript and it works like a charm in either Illustrator or Inkscape.

I find this approach quite useful when I want to annotate plots with greater precision and control than is possible in R.