The Scientific MethodThe Scientific Method

The The Scientific MethodScientific Method

is a is a problem solving-problem solving-strategystrategy. .

*It is just *It is just a series of stepsa series of steps that can be that can be used to solve any problem.used to solve any problem.

Step 1: State the ProblemStep 1: State the Problem *Before you can begin to think of an *Before you can begin to think of an

experiment, you have to know what experiment, you have to know what you want to know an answer to. you want to know an answer to. Often, scientists will ask a question.Often, scientists will ask a question.

In this step, a scientist will In this step, a scientist will figure out figure out exactly what they want to knowexactly what they want to know. .

EXAMPLE: EXAMPLE:

Step 2: Gather InformationStep 2: Gather Information

*Before you can find the answer to a *Before you can find the answer to a question, you must figure out what question, you must figure out what you already know. you already know.

In this step, scientists will In this step, scientists will do do research on their subjectresearch on their subject. .

EXAMPLE: EXAMPLE:

Step 3: State a Step 3: State a HypothesisHypothesis

*This is an answer to the question. It is *This is an answer to the question. It is more than just an educated guess. It is more than just an educated guess. It is actually what you think the best answer is actually what you think the best answer is after you have done some research.after you have done some research.

In this step, In this step, scientists state their solution scientists state their solution to the problem, or their answer to the to the problem, or their answer to the questionquestion..

EXAMPLE: EXAMPLE:

Step 4: Test the Step 4: Test the HypothesisHypothesis

*Just because you come up with an answer, *Just because you come up with an answer, it does not mean it is the best answer. it does not mean it is the best answer. Somehow, you have to do something to Somehow, you have to do something to prove that your hypothesis is correct.prove that your hypothesis is correct.

In this step, scientists In this step, scientists design experiments design experiments to prove that their hypothesis is correct. to prove that their hypothesis is correct. Then they will do the experiment and Then they will do the experiment and gather data.gather data.

EXAMPLE: EXAMPLE:

Step 5: Step 5: Record and Analyze the Record and Analyze the

DataData *After an experiment, you might have a *After an experiment, you might have a

stack of surveys or a bunch of numbers. stack of surveys or a bunch of numbers. These need to be organized into data These need to be organized into data tables, charts, and graphs before any tables, charts, and graphs before any patterns, trends, or relationships can be patterns, trends, or relationships can be seen. In this part, it is important to note all seen. In this part, it is important to note all possible observations that relate to the possible observations that relate to the experiment.experiment.

In this step, scientists In this step, scientists organize the organize the information they collected in data tables, information they collected in data tables, charts, and graphs.charts, and graphs.

EXAMPLE: EXAMPLE:

Step 6: State the Step 6: State the ConclusionConclusion

*After you have analyzed the information *After you have analyzed the information you gather, you are able to say of your you gather, you are able to say of your hypothesis was right or not. If you are hypothesis was right or not. If you are right, say why. If you are wrong, try to right, say why. If you are wrong, try to figure out why or think of other answers to figure out why or think of other answers to the problem that other scientists may the problem that other scientists may want to try.want to try.

In this step, scientists In this step, scientists state if their state if their hypothesis was correct or not and explain hypothesis was correct or not and explain how their experiment proves this.how their experiment proves this.

EXAMPLE: EXAMPLE:

Step 7: Repeat the WorkStep 7: Repeat the Work *After an experiment is complete, scientists will *After an experiment is complete, scientists will

often repeat them for different reasons. If the often repeat them for different reasons. If the hypothesis was right, someone may try the whole hypothesis was right, someone may try the whole experiment again, just to verify the results. If the experiment again, just to verify the results. If the hypothesis was wrong, they may try something hypothesis was wrong, they may try something else based on what was stated in the conclusion.else based on what was stated in the conclusion.

In this step, scientists In this step, scientists will repeat the whole will repeat the whole processprocess. This can either be done as a check to . This can either be done as a check to make sure what the scientists say is true really is, make sure what the scientists say is true really is, or to try a completely new hypothesis. or to try a completely new hypothesis.

EXAMPLE: EXAMPLE:

What’s the Point?What’s the Point?

After scientists test their hypothesis, After scientists test their hypothesis, they will report their findings in a they will report their findings in a scientific journal. MOST experiments scientific journal. MOST experiments actually prove the hypothesis wrong. actually prove the hypothesis wrong. BUT, the scientists still report what BUT, the scientists still report what they did so they can show others they did so they can show others what they learned.what they learned.

CONTROLLED CONTROLLED EXPERIMENTSEXPERIMENTS

*Controlled experiments are run to *Controlled experiments are run to

prove a hypothesisprove a hypothesis. .

*Most importantly, there must be at *Most importantly, there must be at least least two different experimentstwo different experiments that that are actually being done.are actually being done.

*When designing the experiment, the *When designing the experiment, the scientist must determine exactly what scientist must determine exactly what they are going to test. Then they have they are going to test. Then they have to figure out how experiment would to figure out how experiment would run under “normal” conditions. run under “normal” conditions. They They have to arrange an experiment to have to arrange an experiment to show how things normally happen.show how things normally happen.

This is the This is the CONTROLCONTROL, , or what they are or what they are using to compare their results to.using to compare their results to.

Basically, Basically, scientists will try to make scientists will try to make their experiment run different from their experiment run different from normal.normal. If they want to make sure If they want to make sure that they are only testing their that they are only testing their hypothesis and that nothing else is hypothesis and that nothing else is affecting the results, affecting the results, they must they must identify only one thing that can be identify only one thing that can be changed.changed. The only thing different is The only thing different is called the called the EXPERIMENTAL EXPERIMENTAL VARIABLEVARIABLE..

TO SUM IT UP:TO SUM IT UP: A controlled experiment actually has A controlled experiment actually has

two “set-ups:” two “set-ups:” The The controlcontrol and the and the experimentalexperimental. . These two set-ups are These two set-ups are exactly the exactly the

same, same, exceptexcept for the experimental for the experimental variable. variable.

There can only be one thing different There can only be one thing different between the set-ups if you want to between the set-ups if you want to prove that the variable is actually prove that the variable is actually making a difference.making a difference.

POINTS TO REMEMBER:POINTS TO REMEMBER: *To make sure results are accurate, *To make sure results are accurate,

experiments should be done many experiments should be done many times, or with a large sample size. times, or with a large sample size. This is because there is always This is because there is always something different each time. something different each time.

The more tests that are done, the The more tests that are done, the closer you can get to an “average” closer you can get to an “average” result. result.

*The word “variable” means *The word “variable” means many things. Keep it straight.many things. Keep it straight.

THETHE VARIABLE VARIABLE In controlled In controlled

experiments, it is the experiments, it is the only difference only difference between the control between the control and the experimental and the experimental set-up. set-up.

http://collections.ic.gc.ca/island/woodlandplants.htm

http://www.music.columbia.edu/~douglas/portfolio/how_to_annoy_a_plant/

EXPERIMENTAL VARIABLESEXPERIMENTAL VARIABLES Things that change or could change in an Things that change or could change in an

experiment. experiment. CONSTANT VARIABLESCONSTANT VARIABLES

All factors that could change, but should be the same.All factors that could change, but should be the same. EX: Sunlight, water, soil, living conditions, food, types of EX: Sunlight, water, soil, living conditions, food, types of

plants/ animals being testedplants/ animals being tested INDEPENDENT VARIABLE (Manipulative) INDEPENDENT VARIABLE (Manipulative)

A measurable quantity in an experiment. The scientist has A measurable quantity in an experiment. The scientist has control over these values and can be set up ahead of time control over these values and can be set up ahead of time on a graph.on a graph.

EX: Time –the experimenter decides if it will be collected EX: Time –the experimenter decides if it will be collected every minute, every 5 minutes, etc. This can be plotted on every minute, every 5 minutes, etc. This can be plotted on a data table and/or graph well before the experiment a data table and/or graph well before the experiment happens.happens.

DEPENDENT VARIABLE (Responding)DEPENDENT VARIABLE (Responding) Another measurable quantity in an experiment. This is Another measurable quantity in an experiment. This is

often the reason for doing the experiment. This is the often the reason for doing the experiment. This is the information you want to know and the values can not be information you want to know and the values can not be plotted ahead of time. plotted ahead of time.

EX: Temperature –This often EX: Temperature –This often dependsdepends on how long the on how long the experiment has been running. experiment has been running.

In a controlled In a controlled experiment, you experiment, you must explicitly keep must explicitly keep all variables constant all variables constant except the one you except the one you are manipulating. are manipulating. For instance, if you For instance, if you want to test want to test response to wet vs. response to wet vs. dry conditions, the dry conditions, the light, temperature, light, temperature, chemicals in the chemicals in the filter paper or on the filter paper or on the dish surface, and dish surface, and movement of the movement of the table must all remain table must all remain constant. In addition, constant. In addition, all the experimental all the experimental organisms must be organisms must be of the same of the same approximate age, approximate age, size, and state of size, and state of health.health.

It is not enough to say It is not enough to say you will hold all variables you will hold all variables constant; you must explain constant; you must explain how you will do this, and how you will do this, and do it!do it!

http://www.phschool.com/science/biology_place/labbench/lab11/control.html