5. Experimental Procedure

Writing your Experimental Procedure

     A procedure is the detailed steps of the experiment. The procedure must be clear, and should include the list of materials and how they were used. It should also be detailed enough for another scientist to be able to follow the procedure and complete the experiment without having to ask for help or direction.

     The procedure is how you plan to do things, in short, how you are going to conduct your experiment. An experiment can only have one variable, which means you can only change one condition. For example: within the plant growing experiment that was discussed earlier, only the types of water that are given to the plants can be changed. The types of soil, light, temperature, or plant foods cannot be changed in any of them. They must all be treated the same way at all times. If there is more than one variable (or thing changed), the experiment becomes flawed. It can be hard to figure out what other conditions must stay the same, it may help to think it through before you start your experiment.

     Also 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 decide on a procedure that will take months to carry out. Think about your “sample size” ; how many plants will you test with each type of water? Allow a big enough sample (at minimum of 3 in each) so you can have an average growth recorded for each group. 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.  It's also a good idea to have someone else read your procedure over, as they may be able to help you determine if something is not completely clear.

Criteria for Writing a Procedure:

• Includes detailed steps of the experiment. (Like game rules.)

• Written clearly, with little doubt of what to do next

• Includes the list of materials, amounts, and how they are to be used

• Should be able to be followed by anyone

• Outlines what observations should be made and what data should be collected

• Defines the number of trials to be done. (Minimum of three.)

  • Increasing the number of trials, increases the validity of the results

• Includes and identifies the manipulated/changed (independent) and responding/measured (dependent) variables

Variables & Hypothesis Worksheet

General & Safety Regulations