Scientific Method

By Moira Whitehouse

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Complemented by my slideshow Scientific Method Variables

We introduced the variables used in the Scientific Method in a previous presentation. Let’s think back about what was covered in that presentation.

Do you remember what the Scientific Method is?

1. One way scientists find out about the world around us.

The scientific method is:

2. A method that scientists use to answer specific questions.

If a cat always lands on its feet and... when you drop your toast it always lands butter-side down.... what happens when you tie a piece of buttered toast to a cat’s back.*No cats were harmed in this thought experiment.

For example:

VARIABLE

In order to understand the Scientific Method, we first need to know what a

is.

Do you… remember… what a variable is?

Yes, a variable is

anything in an experiment that can change. Remember there are three types of variables. What do you recall about these three variables?

… a change variable?…a

responding variable?

…a control variable?

… a change variable?

Let’s start with:

Change variable—the thing the experimenter changes on purpose.

…a

responding variable?

Then comes:

Responding variable-- what the experimenter observes or measures to see if the change variable is making an difference.

…a control variable?

And finally:

The control variable: all the other things that could cause the responding variable to change—must be kept the same.

One more thing to remember:The experimenter always starts with a

that can be answered by changing a variable and observing the results.

? ?? ?? ? ?question ?

Now let’s look at the steps in the Scientific Method.

The first step in this and any experiment is coming up with a

Problem

1. Problem• Is a question • Is made up of the change and responding variable

Jane knows that plants need light to grow. But she wonders—what about seeds. Do seeds need light to sprout? She decides to design an experiment to answer her question.

So in Jane’s experiment with the seeds what will her change variable be?

Yes, it will be whether or not the seeds receive light.

What could her responding variable be?—what could she observe or measure to see whether or not seeds need light to sprout or grow?

She plans to put 3 seeds in light and 3 seeds in the dark and then count the number of seeds that sprout when light is present and the number when light is not present.Now that we have the change variable (light and dark) and the responding variable (the number of seeds that sprout), let us write the problem—the question with the change and responding variable.

Will more seeds sprout in the light than in the dark?

or

Does light affect the number of seeds that sprout?

After you come up with a Problem, the next step in the Scientific Method iscoming up with:

The Hypothesis.

2. Hypothesis • Answers the question

• Predicts what will happen

What do you think? Will more seeds sprout in the light or in the dark?

What will be the hypothesis for Jane’s experiment with light and sprouting seeds?

Because plants need light to grow, Jane thinks seeds will also need light to sprout. So her hypothesis will be:More seeds will sprout in the light than in the dark.

This plan is called

The Procedure

After coming up with an Hypothesis, the experimenter writes out a plan to test the Hypothesis.

3. Procedure • Steps to be taken to test the hypothesis

• Includes control variables

What would be some of the control variables in Jane’s experiment. What besides light might affect how many seeds sprout?Jane thinks seeds need light to sprout. On the next slide, you will see the step by step plan that Jane came up with to test her hypothesis.Circle the change variable in red, the responding variable in green and underline the control variables in purple.

1. Find 10 identical potting containers and fill them with the same type of potting soil. Place 3 pinto bean seeds in each potting container on top of the soil-- don’t cover the seeds with soil.2. All ten of the pots are to be placed in the same area, getting the same amount of sunlight for two weeks, but:3. Cover 5 of the pots with black paper bags so that the seeds receive no light except when watered.

5. After two weeks count the number of seeds that have sprouted (started to grow) in each pot.

4. Each day pour 15 mL of tap water into each pot.

Did your product look like this?

1. Find 10 identical potting containers and fill them with the same type of potting soil. Place 3 pinto bean seeds in each potting container on top of the soil-- don’t cover the seeds with soil.2. All ten of the pots are to be placed in the same area, getting the same amount of sunlight for two weeks, but:3. Cover 5 of the pots with black paper bags so that the seeds can receive light only when watered.

5. After two weeks count the number of seeds that have sprouted (started to grow) in each pot.

4. Each day pour 15 mL of tap water into each pot.

Once the experimenter has come up with a step-by-step procedure, he or she gathers the materials and conducts the experiment.

As an experimenter conducts the experiment, he or she records the observations or measurements (data) in a data chart.

To make sure that the results did not occur due to chance, an experimenter repeats the experiment several times collecting data each time.

Trial 1 Trial 2 Trial 3 AverageLight 3 seeds 3 seeds 3 seeds 3 seedsNo Light 3 seeds 3 seeds 3 seeds 3 seeds

Here are the results of Jane’s experiment as shown in a data chart.

The number of seeds that sprouted

Sometimes the results are also shown in a graph.

After conducting the experiment and gathering the data using the steps in the Procedure, the experimenter

4. analyzes the data

Trial 1 Trial 2 Trial 3 AverageLight 3 seeds 3 seeds 3 seeds 3 seedsNo Light 3 seeds 3 seeds 3 seeds 3 seeds

The number of seeds that sprouted

Let us analyze Jane’s data.

We see that all seeds sprouted in both the light and in the dark.

5. Conclusion

After analyzing the data, the experimenter comes up with a

• answers the question allowing the experimenter to decide if the hypothesis is right or wrong.

• answers the question.

The conclusion

•experimenter decides if the hypothesis is right or wrong.

So what can Jane conclude?

From her data, Jane can conclude that seeds DO NOT need light to sprout.

and ask a question

Scientific Method in review

Make an observation and ask a question

Is this good to eat?

Problem

Make an hypothesis.

This will be good to eat and will be tasty.

Conduct the experiment and collect the data.

Procedure

Analyze the data

Does it taste good?

Draw a conclusion.

It tastes awful! It is not good to eat.

Share your results and ask someone else to duplicate your experiment.

Try this and see if you think it tastes good.

Steps in the Scientific Method

• Problem

• Hypothesis

• Procedure

• Analyze data

• Conclusion