Yesterday for Journal Club we read a paper by Coley et al (2006) for Journal Club titled "The effects of plant quality on caterpillar growth and defense against natural enemies". Although I think we all enjoyed the read, most of our discussion revolved around aspects of the paper that we found problematic. Among the problems we discussed, was one that made me think of what we are and will be learning in Biostats and Experimental Design.
The researchers had opportunistically captured 85 species of caterpillars on 40 different species of plants. The researchers also noted weather the leaf they found the caterpillar on was young or old. The caterpillars were then reared on the same species of plant and the same age of leaf that they had been found on for the remainder of the experiment in order to assess growth rates.
One problem that was brought to my attention by a faculty member, who had reviewed the paper before it went for publication, was that the researchers used an ANOVA to evaluate the caterpillar growth rate data. She explained that an ANOVA was inappropriate because the caterpillars were never randomly assigned treatments. Instead, they were reared only on the plant and leaf age they were found upon, without ever testing to find out how the various species would develop on other, random plant assignments.
I look forward to learning more about how to apply ANOVAs and to the day when I might actually understand how to apply them to my own studies. It is a bit intimidating to know that even very experienced researchers sometimes aren't sure which statistical analyses are best fit for their data!
References:
P. D. Coley, M. L. Bateman, T. A. Kursar (2006) The effects of plant quality on caterpillar growth and defense against natural enemies Oikos 115 (2), 219–228.
Subscribe to:
Post Comments (Atom)
2 comments:
Just out of curiosity, have you used ANOVA in your own statistical analyses? Or are you planning to? If so, what sort of data have you used? Thanks, I was just interested in learning what graduate students use on a regular basis!! In my undergraduate experience, I have never used it, but maybe in the future I will.
Good description of the paper - and way to go with the lit cited, too! Lee would be pleased :)
I'm not sure whether it's intimidating or reassuring that experienced researchers don't always know the best analytical techniques. On the one hand, I'd like to think that there is some "right" test for any dataset, and that somehow as full-fledged biologists we will all know what this is. On the other hand, I'm glad I'm not the only one sitting here scratching my head!
Keep up the great work! I really appreciate your thoughtful insights in this class and others.
Cheers,
Nicole
Post a Comment