The Scientific Method
Do you like detective or mystery stories? Why do you like them?
Detectives and investigators decipher the clues and try to figure out a logical
explanation for what happened and, above all, who did it! Or do you like to
play games that make you think and figure out a strategy or an answer? If
you enjoy mysteries and figuring out answers to questions or problems, then
the chances very good are you already know something about the scientific
method. It’s just that you haven’t called it the scientific method yet.
The scientific method is basically an organized way to investigate
something that interests you, when you want to find out why something
happens the way it does. The scientific method starts with a question.
Because the method is scientific, the question you ask needs to be something
you can measure so you can compare results you are interested in. Maybe
there’s already a good answer to your question so it’s important to do
background research, looking in the library or searching through the Internet
to find out what’s already written about your question.
Just like a detective might come up with a list of suspects who might
be responsible, the next step in the scientific method is to formulate a
hypothesis. This hypothesis is an educated guess about how the things
you’re asking about actually work. For example, “If I give my plants fertilizer
in the spring, they will have more flowers.” is a simple hypothesis about how
plants grow. An important part of formulating a hypothesis is making sure it
is something you can measure. In this example, you can count the number of
flowers. What are some of the other “suspects” that might be responsible for
plant growth? Did you come up with water, light and temperature? Take a
moment to write some other hypotheses (plural of hypothesis) about plants.
The next step in the scientific method is to show that the hypothesis is
correct (true) or incorrect (false). When scientists are doing research into
complicated areas of science, many of their hypotheses are false. Scientists
are patient and persistent and keep looking for answers. The way to show
that a hypothesis is true or false is to design and complete an experiment.
Scientists must be careful in how they design an experiment to make sure
that it tests exactly what the hypothesis states. A proper experiment
compares two or more things but changes only one variable or factor in the
experiment.
In an experiment, one group is the control group and the other is the
experimental group. If a scientist was testing the flower and fertilizer
hypothesis, she would select one species of flower to test with and buy a
dozen plants. Six of the plants would be the control group and six the
experimental group. All the plants would be kept in the same greenhouse
and given the same amount of light and water. The experimental group
would get a measured amount of fertilizer on a regular schedule while the
control group would not get any fertilizer. The scientist would write down
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everything that she did, keeping good records in a laboratory notebook.
Keeping detailed accurate records is an important part of the scientific
method.
The scientist would conduct this flower experiment for a few weeks
until the flowers bloomed. Then she would count the number of flowers in the
control group and compare it with the number of flowers in the experimental
group. Real science experiments use hundreds or thousands of experimental
subjects to insure that the results apply to more than just a few subjects.
The next step in the scientific method is to analyze the results.
Scientists use sophisticated statistics, a type of mathematical analysis, to
analyze results. Different kinds of statistics are used in different fields of
science. Simply using numbers from an experiment will not prove scientific
hypotheses in real science experiments.
Let’s look at the flower example again. What if the control group
produced 20 flowers and the experimental group produced 40 flowers. In this
case, since the difference in the number of flowers is huge, you might draw
the conclusion that the fertilizer did increase the number of flowers and your
hypothesis is true. What if the control group produced 20 flowers and the
experimental group produced 23 flowers? Just because 23 is larger than 20
doesn’t mean that the fertilizer improved the number of flowers. There
weren’t enough subjects (plants) in this experiment to determine that. But
with lots more subjects and using statistics, a scientist could conduct a valid
experiment that shows the difference between 20 and 23 flowers is due to
the fertilizer. Whether a hypothesis is true or false isn’t decided by the
measurement numbers themselves but by the statistical analysis.
After scientists complete an experiment they report their conclusions.
Each branch of science has a report format for publishing the results of
experiments. If you do an experiment for a science fair project you will
report your conclusions on a poster board for everyone to see. Your school
probably has a format for science fair posters just like scientists have report
formats.
What happens if the experiment does not show that the hypothesis is
true? Does that automatically mean that the hypothesis is false? Absolutely
not! Scientists are persistent in their research and will try another slightly
different experiment. In the flower example, maybe we didn’t use enough
fertilizer to make a difference. Maybe we didn’t use the right kind of fertilizer
for the kind of plants we used. The next step might be to run another
experiment with a larger amount of fertilizer. Repeating experiments or
setting up new experiments to pinpoint the real relationship underlying the
question we’re trying to answer is called an iterative process.
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Overview of the Scientific Method
Step 1:
What is the problem?
(Ask it as a question)
|
Step 2:
Form a hypothesis
(What to find out)
|
Step 3:
List materials needed
|
Step 4:
Define the procedures
(Steps in experiment)
|
Step 4:
Analyze the results
|
Step 6:
Form a conclusion
(State it clearly)
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Name: __________________________________ Date: ______
Understanding the Scientific Method
The scientific method has the following steps:
1.
2.
3.
4.
5.
6.
7.
Ask a question
Form a hypothesis
List materials needed
Decide the steps in the procedure
Perform the experiment
Analyze the results
Draw a conclusion
Sheryl’s Mom works third shift so she sleeps during the day. Sheryl and her
friends like to listen to loud music after school but they don’t want to disturb
Sheryl’s Mom. Put the step number next to each step of the scientific method
for this problem.
_____ She plans to stand outside her Mom’s room and measure the sound.
_____ She knows she needs her CD player and the loudest CD she likes.
_____ Sheryl wonders how loudly she and her friends can play music
without disturbing her Mom.
_____ Sheryl decides that half volume is still too loud.
_____ She plans to turn on the CD player in the rec room with her CD
at at half volume.
_____ One day when her Mom isn’t sleeping, Sheryl tries the experiment.
_____ Sheryl thinks that half volume should be low enough.
_____ Standing outside her Mom’s room she can still hear the music.
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Name: __________________________________ Date: ______
Practice with the Scientific Method
The scientific method has the following steps:
1.
2.
3.
4.
5.
6.
7.
Ask a question
Form a hypothesis
List materials needed
Decide the steps in the procedure
Perform the experiment
Analyze the results
Draw a conclusion
In 1872 a wealthy railroad tycoon named Leland Stanford (Stanford
University is named after him) made a bet with a friend about a galloping
horse. Put the step number next to each step of the scientific method for this
problem.
_____ Mr. Stanford proposed that the hooves of a galloping horse don’t
touch the ground at some point in time during the gallop.
_____ Before there were digital cameras the film in the camera needed to
be developed into pictures.
_____ A racehorse, a jockey and a camera
_____ Some of the pictures showed that the horse’s hooves were all in the
air at the same time.
_____ Leland Stanford made a bet that the hooves of a galloping horse
don’t touch the ground at some point in time.
_____ Mr. Stanford decided to ask a photographer to take pictures of a
horse galloping at the racetrack.
_____ The jockey rode the galloping horse around the racetrack.
_____ Mr. Stanford looked at the pictures the photographer brought him.
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Name: __________________________________ Date: ______
Historic Scientific Method
The scientific method has the following steps:
1.
2.
3.
4.
5.
6.
7.
Ask a question
Form a hypothesis
List materials needed
Decide the steps in the procedure
Perform the experiment
Analyze the results
Draw a conclusion
Gregor Mendel was an Austrian monk who lived from 1822 until 1884. He
performed some of the first research ever in heredity. Mendel grew an
estimated 28,000 pea plants over eight years. Students can perform an
experiment that is similar to one of his famous experiments with pea plants.
_____ Mendel proposed that cross-bred pea plants will show specific
characteristics from each parent.
_____ Two kinds of purebred pea plants, a place to grow crossbred plants
_____ Mendel thought that heredity depended on both parents and that
specific characteristics from each parent were passed on.
_____ Mendel analyzed the characteristics of the peas produced by the
crossbred plants.
_____ Cross-pollinate the purebred pea plants
_____ Grow the crossbred pea plants until they mature
_____ Mendel determined that there are dominant and recessive traits in
crossbred pea plants.
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Answers
Understanding the Scientific Method
_4___ She plans to stand outside her Mom’s room and measure the sound.
_3 ___ She knows she needs her CD player and the loudest CD she likes.
_1 ___ Sheryl wonders how loudly she and her friends can play music
without disturbing her Mom.
_7___ Sheryl decides that half volume is still too loud.
_4___ She plans to turn on the CD player in the rec room with her CD at
at half volume.
_5 ___
One day when her Mom isn’t sleeping, Sheryl tries the experiment.
_2___
Sheryl thinks that half volume should be low enough.
_6___
Standing outside her Mom’s room she can still hear the music.
Practice with the Scientific Method
_2___ Mr. Stanford proposed that the hooves of a galloping horse don’t
touch the ground at some point in time during the gallop.
_4___ Before there were digital cameras the film in the camera needed to
be developed into pictures.
_3 ___
A racehorse, a jockey and a camera
_7___
Some of the pictures showed that the horse’s hooves were all in the
air at the same time.
_1 ___ Leland Stanford made a bet that the hooves of a galloping horse
_4___ don’t touch the ground at some point in time.
Mr. Stanford decided to ask a photographer to take pictures of a
_5 ___ horse galloping at the racetrack.
_6___ The jockey rode the galloping horse around the racetrack.
Mr. Stanford looked at the pictures the photographer brought him.
Historic Scientific Method
_2___ Mendel proposed that cross-bred pea plants will show specific
characteristics from each parent.
_3 ___ Two kinds of purebred pea plants, a place to grow crossbred plants
_1 ___ Mendel thought that heredity depended on both parents and that
specific characteristics from each parent were passed on.
_6___ Mendel analyzed the characteristics of the peas produced by the
crossbred plants.
_4___ Cross-pollinate the purebred pea plants
_5 ___ Grow the crossbred pea plants until they mature
_7___ Mendel determined that there are dominant and recessive traits in
crossbred pea plants.
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