On Wednesday last week we learned the mechanics of standard deviation. We worked with small data sets. I listed the steps on the board. The same steps were listed in their book. With an example. We practiced in class. They verified their results with their groups. I felt good sending them home with a few more problems to try on their own.
The next day, first period went well. The vast majority of the students had the right answers. Those that didn’t asked good questions and corrected their homework. We started discussing what the standard deviation tells us. Getting into the meaning. Interpreting. Discussing how it applied to the unit problem. I walked into 5th period confident that things would go just as well.
I was wrong.
Half of the students had major errors. They seemed to have invented a new method for computing standard deviation. My plan went out the figurative window. It seemed that understanding was limited to certain groups of students, so the “go over the steps with your group” method wasn’t going to work. I didn’t want to redo what we had done the day before for two reasons. One – it obviously didn’t work for half of them. Two – it did work for the other half and I didn’t want to bore them.
So, I punted. “Okay, everyone who got the answers right, find someone who didn’t and show them how to do this. You have ten minutes. By then everyone should know how to find the standard deviation. Make them show they know how to do it. Go.”
Chaos appeared to ensue. Students were all over the place. It was loud. I walked around and put in my two cents where it was needed. Which was mostly to say, “That’s not math talk.” The teacher next door later jokingly complained to me – our math was too loud.
The quick quiz on Friday shows that most of them seemed to get it. There were more minor arithmetic errors than I would have liked (subtracting whole numbers? ). Only two had major conceptual errors. A bit of clean up tomorrow and we’re ready to move on.