Bond with James: Accuracy & Precision with Wacky Rulers

Tuesday, August 18, 2015

Accuracy & Precision with Wacky Rulers

The concept of measurement in science, especially in chemistry or physics, is an important skill students need to acquire early on in the school year.  I am going to share a simple engagement strategy in regard to accuracy and precision that I have used in the past with my students. This is also a great activity to implement the first week of school if students are not able to conduct labs without a signed safety contract. 

My former mentor and instructional coach used to let me borrow a set of non-traditional rulers - which I nicknamed bumble bee rulers because they had an alternating yellow and black box pattern on both sides of the ruler (I will refer to them as wacky rulers from here on). 
Unfortunately, my coach could not remember where she got the rulers from and retired from the profession; however, I created my own version of the ruler and call them wacky rulers.

I would give each student a ruler and a picture as soon as they entered the class. My directions were simple - measure the object and write your answer on a Post-It note. Some students would look at me weird and some would ask me what units they were supposed to use. Others would try to figure out which end of the ruler to use.
I created this version just to mess with the students but it does come in handy when comparing different measuring instruments and talking about accuracy and precision. 

Each student would then place their Post-It note on chart paper or the board (or you can have them write directly on the chart paper or board). I would get a variety of measurements (e.g. 4 squares, 3 blue squares and 2 black squares, 5 boxes, 5.1 boxes, etc.) 

Next, I would have the students measure the object again with a metric ruler and create another poster with the metric ruler measurements. 

At this point, I would have two class sets of measurements - one from the wacky ruler and another from the metric ruler. I would give students an opportunity to discuss in pairs, or a group of 4, which ruler they believed was the best instrument for measuring.  I would also give students time to discuss their thoughts about the varying measurements with the wacky ruler; as well as how the measurements differed between the two rulers.  

This is also a great opportunity to explain that a measurement consists of a number and a unit. Additionally, it also is a great time to introduce and discuss accuracy and precision by utilizing the class measurements. You could have students copy the actual measurements in their interactive notebooks and write a brief reflection summarizing the activity. I really like using the wacky ruler data when speaking about the precision of our measurements since, from my experience, the data usually is all over the place. ;)  For the sake of explaining accuracy, I will tell students that my measurement is the true/accepted value. My students usually understand the difference between accuracy and precision from this point forward.  

I should note that this is usually a 10-15 minute activity / discussion at the start of class (warm-up and engagement).  I also incorporate significant figures, however, I will be writing another post on that later as I incorporate an accuracy, precision, and sig fig lab activity in the same lesson (and sometimes use it as a lab practical).  You may have also seen my collaborative posters floating around Pinterest or other sites. That is another collaborative activity I integrate into this particular measurement unit. 

If you want a copy of the wacky rulers, you may download it for FREE here. I have included the image of the shark seen in this post and a slightly editable 10 slide PowerPoint file.

Please share if you have any ideas similar or different from this; or if you try this and your experience with it. As always, thanks for reading! :)


  1. This sounds like a great way to get them talking and thinking about accuracy, precision, AND the importance of including units with a measurement. TFS!