PMean: Peer grading in Introduction to R, SPSS, SAS

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I’ve gotten some helpful feedback that I need to encourage more interactions among students in the on-line classes, Introduction to R, Introduction to SPSS, and Introduction to SAS. No just interactions of the students with the teacher, but interactions between the students.

In many online classes this is done by encouraging online discussion of the material in the class. This is not so easy, however, for these three classes. I can just imagine myself posting the following on Blackboard. “Tell me what you think about the read.csv function in R.”

There are a couple of ways, however, that make sense for technical classes like these.

An obvious strategy is to encourage students to comment on anything they find confusing in the videotaped lectures. For example, as student might say

“I got a strange error message when I tried to import the dataset with “read.csv(file=fn, header=TRUE)”

When you see this, rather than answer it right away, ask

“Did anyone else have this problem?”

Then wait a bit. If you’re lucky, another student might chime in and say

“I had that problem also, but when I stripped the first line from the file, and changed the option to “header=FALSE” it worked just fine. Except, I lost the variable names for each of the columns of data.”

Then another student might chime in and say

“I got the variable names back by cut-and paste of the first line into the R program itself. I had to reformat a bit, but it worked nicely.”

That’s the theory, anyway. It mimics the situation in a class where one person asks a question, and another student answers the question before the instructor can (which is ideal from the instructor’s perspective).

Now, it is hard to get students to offer commentary, either online or in a live class, but that’s something that you need to encourage if you want to be a good teacher. I must confess that I am not nearly as good at this as I should be. I tend to dominate any classroom discussion, to the detriment of myself and my students. But I’m working on it.

Another strategy for encouraging student interactions is to require peer-grading of assignments. These are pass/fail classes, so I’m not interested in a grade per se. What I want is some helpful commentary about the good things and bad things in another student’s assignment.

Again this is tricky for a programming class. Someone shares the code they used and the output that the code produced, and what is there to comment on other than the trivial comment that it worked.

One thing that you can get one students to critique about another student’s work is the quality of the documentation. One thing these classes need to emphasize more is placing a greater emphasis on documentation.

So a student might submit a project where they imported a text file, created value labels, and recoded obvious outliers as missing values. The first student submits their code and output, but also their data dictionary and their changelog. The second student provided feedback by answering the questions

  1. Did you understand the information in the data dictionary?
  2. is there any information that you wanted to see in the data dictionary that wasn’t there?

In order for peer evaluation to work at its best, you need to make sure that the second student is not working on the exact same data set that the first student is working on. It’s easy to overlook a poorly documented data dictionary for a data set that you’re already intimately familiar.

Fortunately, there are so many open source data sets out there that it won’t be hard to give each student a different data set to work on.

A second thing that one student can critique about another student’s work is the quality of the interpretation of the output. This requires a change in emphasis again. These classes do ask for interpretations when appropriate, but when the output is just a two by two crosstabulation like

       Dead Alive
Female  154   308
Male    709   142

there’s only so much you can say. So these classes need to incorporate things like a Fisher’s Exact Test for any two by two crosstabulation, so that students can say that males have a statistically significant increase in mortality in this data set compared to females.

I don’t want to go too deeply into statistical tests in these classes. My goal is to teach coding, not statistics. But adding a few more tests and confidence intervals, very simple ones, will allow for more interesting interpretation of the output.

So assignments should ask for the output and the code (for R and SAS) and the log (for SAS). But it should also ask for a brief report (no more than one page) interpreting the results. When the first student submits the report, ask the second student to address the following questions

  1. Did you understand the interpretation provided?
  2. Was it consistent with the raw output?
  3. Was there anything else you wanted to see in the interpretation?