So variable

Part of design inquiry is being able to deconstruct a problem and brainstorm variables that impact on each other.

The simple yet highly effective variables grid is useful across all year levels and multiple subjects in open ended investigations.

Here’s how you use it in:

In the centre square write the variable you want to measure (M) i.e. the dependent variable e.g. distance ball thrown (in metres).

Around the outside squares, brainstorm and list any factors that could change that. E.g. height of person throwing, type of ball, wind conditions, muscle mass of throwing arm, dominant or non-dominant arm, run up or standing throw etc

Once as many factors have been brainstormed as possible, use the variables grid to design a fair test.

The centre square is the dependent variable.

Pick one of the outside squares to investigate as the independent variable.

All other outside squares must be controlled, assumed to be constant or kept the same to ensure a fair test.

Design Inquiry Skills

We have investigation folios in many subjects within the Australian Curriculum – where tasks require students to deconstruct problems, pose questions, perform investigations, evaluate methods and write justified conclusions.

As part of our Design Inquiry Series, we highlight some tried and tested strategies for building the skills of design inquiry in class, especially in science.

Check out each of the posts in the series through the links below:

0. It’s not fair

– teaching the concept and purpose of fair tests

1. So variable

– how to use a variable grid to deconstruct a problem and plan for a fair test

2. Building critical evaluation skills

– Use a MER chart to logically and critically evaluate the method and suggest improvements.

M – method

E – errors

R – recommendations

3. Getting a good conclusion

– Use the CER format to write a justified conclusion based on the results.

C – claim

E- evidence

R- reasoning

It’s not fair


Sometimes it’s hard to emphasize the importance of having a fair test, when the experiments that students do are a little abstract and don’t seem to change even if they are sloppy in controlling variables.

This classroom demonstration of fair tests requires 2 tennis balls, a basketball, a blindfold and a bin or bucket (empty).

This classroom demonstration clearly teaches the importance of fair tests and will have students calling out “it’s not fair!”.

Ask for a volunteer. Tell the class you want to see who is better at throwing a ball in the bin – you or the student.

Give the student a tennis ball and have them stand about 5m away from a bin or bucket. Take the basketball and stand next to them.

Ask the class who they think will get the ball in. (But it’s not fair!)

You’re a reasonable teacher – you understand you had an unfair advantage with a larger ball. Concede defeat and take a tennis ball, but stand 1m away from the bin.

Ask the class who will be the better shot now. (But it’s not fair!)

Fine, you say, the ball size has to be kept the same and the distance from the bin has to be kept the same. Let’s make this a fair test.

Move to stand next to the student, but blindfold them.

It’s fair, you say. We’re the same distance away, we have the same ball. (It’s not fair!)

OK, you admit. It’s not fair. I’ll take the blindfold off. Now is it fair? (Hopefully, yes!)

This is a reminder to keep the way you measure (the distance from the bin), the equipment you use (size of ball) and the conditions (blindfolded or not) of the experiment the same to be a fair test. Only change one variable and aim to keep all others controlled or the same.

Thanks to the creative Mr Culley for this teaching strategy.

Building critical evaluation skills


Critical thinking is a key life skill that is important to teach students, not only to improve their employability prospects, but to be a critical elevator in life generally.

Within discussion sections of practical reports or investigations, students are often asked to list any errors and suggest improvements or alternate models. This could be within science, or health, maths or any other subject with a critical evaluation report.

Without scaffolding (just providing the usual question prompts), this is the sort of response in a discussion I would get (this is a genuine student response):


1. Errors present in the experiment:


2. Suggested improvements for the experiment:

less hot fire because I burnt myself.

The question prompts alone are not enough support to encourage logical and critical thinking and evaluation of the investigation.

Enter MER. MER stands for Method, Errors, Recommendations. It is a scaffold for logical and critical evaluation (reflecting on and addressing each step where applicable in the method). Having the structure in place also, I find, helps students be creative in thinking up improvements (or recommendations) for reducing errors.

Here’s what a discussion response to errors and improvements looks like using the MER (another genuine student response from the same experiment).

See how using such a simple scaffold can provide for greater depth, support critical thinking, provide scope for greater improvements and technological improvement, and a logical analysis of an investigation.

Getting a good conclusion

In my early years of teaching I would give students a practical report assessment task and tell them to write a conclusion that relates to the aim. I thought this was a reasonable expectation.

However, I would get conclusions handed up that read like this (this is real student work):

The prac was good. It was and well planned. The end result was kind off what I was expecting but it was still good.

Enter CER. CER is a simple yet highly effective strategy for scaffolding a conclusion that gives a logical evaluation of results with a justified conclusion. This is a strategy that works from middle years through to senior years. If used in primary years, students may only use a CE (if they do not have enough science knowledge to do the R). It can be used in science, in maths, in heath/PE or in any subject where a justified conclusion is required.

CER stands for Claim, Evidence, Reasoning.

Under Claim, students restate the hypothesis.

In Evidence, they say if the hypothesis is supported by the evidence, and summarise the results or trends in the data that provide this evidence.

Reasoning is where students give the “why” or the scientific explanation of why that evidence may have been found.

From the same experiment as the above example where “the prac was good”, now students (from the same class and year level) produce a conclusion like this:

The food with the most energy will be the cheese ball followed by the biscuit then by puffed corn. The claim is supported by the evidence. The cheese ball has the most energy with 588 kJ, whereas the puffed corn has the least energy of 42 kJ. This may be because the cheese ball and biscuit were larger and had more sugar than the puffed corn, so had more energy.