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During my first few years as a science teacher, I read more student lab reports than I care to count. I became most interested in the conclusions, because I quickly learned that conclusions could be most reflective of student learning.
In part, I was right. I also found that students simply blamed themselves and their equipment for not getting the results they’d hoped for. In nearly every conclusion, students stated whether or not they’d gotten the results they’d expected. If they did not, their reasoning was human error, faulty lab equipment, or incorrect calculations.
From these statements, I had no idea what might have gone wrong in their work.
We had some class discussions about communication in science. What, exactly, IS “human error?” What was wrong with your lab equipment? And if your calculations “might be wrong,” can you check them again, ask another student, or ask me?
We came up with ways to describe the errors that might be called human error. We found most weren’t actually “human” after all. For example, instead of “we measured wrong,” we might state that we noticed some of the chemical remained stuck to the weighing paper as we transferred it to the reaction beaker. Perhaps some of the product stuck to the stirring rod or to the sides of the beaker when transferring to the filter paper. Perhaps the product was partially soluble and was not caught by the filter paper.
Instead of blaming the lab equipment, we determined if the balance or cylinder had enough precision to measure the amount of chemical we were using. And was the balance zeroed before use? Was the instrument read with the most precision possible? Was the balance pan wiped clean before use? Was the microscope focused on the specimen and not a random piece of debris or an air bubble?
And instead of simply doubting one’s calculations, we could check our steps with another student (or with me!) We could re-run our math through our calculators, checking to see if we were reading and typing measurements correctly. We could evaluate our calculated result for reasonableness, recalling the time I found a student had calculated the mass of a glucose molecule to be 6.50 x 10^28 grams, or more than the mass of Earth.
I now teach students to review their data and observations, make a claim, support it with evidence, and use their science knowledge to reason an explanation for their claim as supported by data.