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Writing the Procedure

[Types of Variables] [Activity #1] [Activity #2] [Activity #3] [Steps to Success] [Move Beyond]

You're doing great! You've chosen a topic and asked a question. You've done a little bit of research and made a best guess as to what the answer might be. Now it's time to design your experiment. The first step is to write the procedure. Once you complete the activities on this page, you'll be well on your way to a complete experimental procedure!

The procedure is a set of very specific instruction about how you are going to conduct your experiment. Consider the image below. What happened to the sandwich on the left?

Image compares a poorly written procedure with a well-written procedure for making a peanut butter and jelly sandwich

Sadly, no one could eat the sandwich on the left. It doesn't even look like a sandwich! The problem is a lack of detail. If you have never made a peanut butter and jelly sandwich, the very precise and detailed directions on the right would be necessary to make the sandwich correctly. Details are the most important part of any experiment because without detail, it would be nearly impossible for someone else to replicate your experiment.

Variables

Details also help to control variables in your experiment. Before you can begin writing the procedure, you need to decide on your independent variable. There are three types of variables to consider:

Independent Variable

The independent variable is the one that YOU choose to help you answer your question. A well designed experiment has only one independent variable. That means you can only change one condition in each experiment. This type of variable is something that you do differently in each trial (i.e. the type of liquid you give each plant changes, the weight of the ball you throw is different each time). Nothing else should change but this one variable.

Controlled Variables

These are all the materials, measurements, and methods that you want to stay exactly the same so that the only thing responsible for change is the independent variable you chose. Every experiment has many controlled variables. These variables should be exactly the same for every trial (i.e. the type of plant used should be exactly the same; the target for the ball is always the same distance away).

Dependent Variable

The dependent variable is the thing that changes as a result of your independent variable, or the one thing that you intentionally changed. This is like cause and effect. What happened (the dependent variable) because of what you changed (independent variable)?

If there's more than one independent variable, the experiment becomes flawed because you can't be sure what caused the changes you observed. It can be hard to figure out what other conditions must stay the same, but it is important to think it through before you start your experiment.

Activity #1: Start Thinking!

description of independent variable, dependent variable, and control

Look at the image to the right. This is Paul's experiment, asking which liquid will help plants grow tallest. The student hypothesized that the plant given soda will grow tallest because plants need CO2, and soda has plenty of that! There are many things this student needs to consider so that the liquid type is the only thing that can affect the growth of the plant.

Take some time to think about how this student might write the procedure for this experiment:

  • What are the controlled variables?
  • What details can the student include to make sure these variables are controlled throughout the experiment?
  • What is the dependent variable?
  • How can the student measure change?
  • What might this student's procedure look like?

Did you think about it? Do you think you know what all the variables are? Click here to see if you found all of them.

Activity #2: It's all in the details!

View this well-written experiment design on Science Buddies, Give It a Lift with a Lever. Take extra time to carefully read through each step in the procedure and consider the questions below.

  1. Do you think you could you follow the procedure? Why or why not?
  2. What controlled variables did you find? What were the independent and dependent variables?
  3. Did you see anywhere that needed additional details? What would have made the procedure better?
  4. Bonus: Follow the procedure and document what happened. Did everything go as planned? Would you change or add anything now that you've completed the experiment?

Ready to check your knowledge? Click here for answers.

Activity #3: Adding Details

It can be tough to jump right into writing a great, detailed procedure, so let's start off easy. Below is a procedure for making lemonade. It's pretty obvious, even to a beginner, that this procedure needs help! Your mission, should you dare to accept it, is to:

  1. Draw a picture of what might happen if you followed this procedure for lemonade, or make a short video using your webcam or video camera.
  2. Rewrite the procedure for lemonade so that it is fantastically detailed. Give your procedure to an adult or peer for feedback. Could they follow your procedure? Was anything missing?

making lemonade recipe

See an example of a detailed lemonade recipe here.

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Ready for some great tips?

section title: steps to successTip #1: Think about how long your experiment will take before you decide on your procedure. If you only have a few weeks to do your experiment, don't write a procedure that will take months to carry out.

Tip #2: Think about your "sample size." How many seedlings will you test with each liquid? A good rule of thumb is to repeat your experiment three times, so allow allow a big enough sample so you can have a few duds in each group, just in case something goes wrong.

Tip #3: Make a list of all of your variables. Make sure you include very specific details to ensure your controlled variables are truly controlled (the same in all trials).

Tip #4: Once you decide on a procedure, write it down step by step. That way, you can prove what you did and can follow the same procedure if you, or someone else, needs to repeat the experiment. Don't forget to include the exact materials you need (i.e. what kind of plant, pot size, etc.), how you'll measure your dependent variable (i.e. the amount plant growth in centimeters), and a chart, journal or other method of recording results and observations.

Tip #5: If you will have a survey for your participants to fill out, get that ready and make plenty of copies. If you will need a chart to write down your test results, make it early, before you begin experimenting. If you take the time to make it look nice with a straight-edge, you can include the actual chart or survey instrument in your project write-up. This really impresses the judges!

Let your teacher know what your question is and how you plan to go about testing it. She may have some good suggestions to save you lots of time and trouble.

Get Started

Now that you've learned all about writing the procedure, variables, and the importance of details, it's time to start writing your own procedure. Before moving on to the next page, take some time to consider your own experiment design. What is your independent variable? What will you be sure to control and keep constant? What materials do you need? Start writing each step in your procedure, including as many details as you can. When you have a rough draft completed, share it with your learning coach or other adult and see if they can follow it. Ask them to look for missing details. Revise your procedure based on your learning coach's feedback, and then move on to the next page to learn how to conduct your experiment.

 

Move Beyond

Below are some great resources to review and enrich! These sites will help you gain a greater understanding of variables and writing a procedure. Make sure you get permission from a responsible adult before visiting any external website!

Science Buddies: Learn about the different types of variables. Examples of each are provided.

Scientific Variables Cartoon: Learn all about scientific variables with a teacher and his student! This fun cartoon makes identifying variables easy!

Lego Activity – Writing a procedure: Build a Lego structure and then write a detailed procedure so that a peer can build the same structure.

Science Buddies – Writing the procedure: Simple explanation for how to write a procedure.

University of Minnesota: Dig a little deeper into the scientific method. Learn how to write an awesome, college level scientific procedure.

Stick Figure Procedures: In this fun video, the importance of accurate, detailed procedures are emphasized as students try to mimic the position of a stick figure.

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Are you a learning coach or teacher? View the lesson plan for this page here.