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Ready, aim, splat!

A plan of action keeps you--not chance--in control of your experiment.

Once you have an idea for an experiment, it's time to take a break. That's right, just sit back and imagine doing your experiment: where you start, what you measure, in what order, and so on.

Remember, if you don't have a clear procedure, a step-by-step plan you can follow, you won't get results you can trust. And other scientists won't be able to understand or duplicate your work.

Say you're experimenting to find out which type of utensil would make the best mashed-potato launcher: a fork or a spoon? (Not that we're endorsing the practice of food fights . . . .) You've already thought ahead enough to decide not to use real mashed potatoes for the experiment, but rather to use a model. (We used "guck" from a toy store.)

You step into a wide-open area with your guck, a spoon and a fork, and start flinging. But if that's all you think about your procedure might look like this:


1. Plop a glob of guck onto spoon.

2. Pull back end of spoon and let go.

3. Measure distance blob flew.

4. Repeat several times.

5. Repeat for fork.

Would you know exactly what to do after reading this procedure? Would two people reading it-say, your "labe assistants"--do the same thing?

Not likely. There's lots of room here for creative interpretation. For example, how are you going to hold each utensil before letting it fire? Will you use the same size glob and same kind of guck each time?

These details are vital. They put you in control by keeping constant any variables that might change your results. So rewrite your procedure to include them.


1. Measure 5g of guck, roll it into a ball, and place it on a 15cm-long plastic spoon.

2. Standing behind a "starting line," hold the spoon handle parallel to the floor, with forefinger knuckle on top of handle and thumb below. (To be absolutely clear on this positioning, why not draw a diagram?)

3. Use forefinger of other hand to pull spoon head back and down to a 15 [degrees] angle.

4. Release the spoon head.

5. Measure distance from starting line to spot where guck hits floor.

6. Repeat Steps 1-5 four more times with spoon.

7. Repeat Steps 1-6 using 15-cm plastic fork.

Now read your procedure and review your steps for accuracy, completeness, and safety. Ask a teacher, parent, or friend to read your procedure and to imagine doing the experiment. Based on their suggestions, revise your steps and add new ones as needed. For example, you may want to have a friend watch and mark the place where the guck hits the floor. Can you find other ways to improve this procedure?

When you think you've got it down, give the experiment a try. If things don't work on this trial run, you can still make changes (use a different model--marshmallows, for example). Just be sure that once you do start collecting data, you follow the same procedure every time.
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Title Annotation:Special Issue: Doing Science; how to develop a plan for an experiment; includes instructions on how to make a data table
Author:Cothron, Julia A.
Publication:Science World
Article Type:Cover Story
Date:Sep 17, 1993
Previous Article:Bursting with project ideas.
Next Article:Real scientists measure metric.

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