Scientific Method Explained
What is Science?
The Goal of Science
1) deals only with the natural world
2) to collect and organize information
3) propose explanations that can be tested
Science – using evidence to learn about the
natural world; a body of knowledge
Science begins with observations – often taking
data on what you see, hear or smell
data– the information gathered from observations
quantitative data = numbers
qualitative data = descriptive
Inference – a logical interpretation based on prior knowledge or experience (Ex. You see a
window broken and a baseball on the floor next to the shattered glass. You can -infer- that a
baseball broke your window)
Hypothesis – a proposed scientific explanation. This statement is testable and can be
confirmed with experimentation or further observation.
Prediction – An if-then statement that shows what you expect to see as a result of an
experiment or observation (Ex. If fertilizer makes a plant grow faster, then seedlings planted
with fertilizer will be taller than the ones planted without fertilizer)
Steps of the Scientific Method
1) Ask questions, make observations
2) Gather information
3) Form a hypothesis
4) Set up a controlled experiment
Manipulated variable – the variable that is deliberately changed (independent variable)
Responding variable is variable that is observed ( aka dependent variable)
5) Record and analyze results
6) Draw a conclusion
7) Repeat
The Scientific Method in Action
Suppose you observed that a cricket outside your window seems to be chirping every night, but some
nights it chirps faster than others. A friend of yours told you once that you can use the sound of a
cricket chirp to tell the temperature. Curious, you decide to design an experiment. First you must
create a hypothesis; here are some examples of possible hypotheses:
The frequency of cricket chirps will change as the temperature changes.
As the temperature decreases, a cricket will chirp fewer times.
Either hypothesis will work, the important thing is that you can -test- the hypothesis by doing an
experiment which will confirm or deny the statement.
To set up the experiment, you go out to your yard and capture a few crickets. You bring them inside
and place them in a container. But wait, if you
have a bunch of crickets together, what if they
chirp based on how many crickets there are
nearby. The goal in designing an experiment is to
eliminate all the variables except the one you are
testing. This means all your cricket subject must be
housed in the same environment (same lighting,
same food, same water..etc). Okay, so you get that
set up and take the temperature of your room. Now
you must wait for the crickets to start chirping. You
count how many times the cricket chirps for a 5
minute period.
Now you have to compare that number with the
chirps that occur at different temperatures. You
may use a heating pad, or ice or any other way to
lower or raise their temperature. You would then
take data for 5 minutes at the new temperature.
In your experiment, the MANIPULATED
VARIABLE is the thing you changed – the
temperature.
The RESPONDING VARIABLE is what you are measuring that happens as a result of that change the number of chirps.
The CONTROL GROUP isn’t obvious in this case – but you can consider your original (room
temperature) data as your control, and the other temperatures your experimental data.
After you have taken data, you can then draw a conclusion about whether your hypothesis is accepted
(correct) or denied (incorrect).
Scientific Method In Action
The Strange Case of BeriBeri
In 1887 a strange nerve disease attacked the people in the Dutch East
Indies. The disease was beriberi. Symptoms of the disease included
weakness and loss of appetite, victims often died of heart failure.
Scientists thought the disease might be caused by bacteria. They
injected chickens with bacteria from the blood of patients with beriberi.
The injected chickens became sick. However, so did a group of
chickens that were not injected with bacteria.
One of the scientists, Dr. Eijkman, noticed something. Before the
experiment, all the chickens had eaten whole-grain rice, but during the
experiment, the chickens were fed polished rice. Dr. Eijkman
researched this interesting case and found that polished rice lacked
thiamine, a vitamin necessary for good health.
1. State the Problem
2. What was the hypothesis?
3. How was the hypothesis tested?
4. Should the hypothesis be supported or rejected based on the experiment?
5. What should be the new hypothesis and how would you test it?
How Penicillin Was Discovered
In 1928, Sir Alexander Fleming was studying Staphylococcus bacteria growing in culture dishes. He
noticed that a mold called Penicillium was also growing in some of the dishes. A clear area existed
around the mold because all the bacteria that had grown in this area had died. In the culture dishes
without the mold, no clear areas were present.
Fleming hypothesized that the mold must be producing a chemical that killed the bacteria. He decided
to isolate this substance and test it to see if it would kill bacteria. Fleming transferred the mold to a
nutrient broth solution. This solution contained all the materials the mold needed to grow. After the
mold grew, he removed it from the nutrient broth. Fleming then added the nutrient broth in which the
mold had grown to a culture of bacteria. He observed that the bacteria died which was later used to
develop antibiotics used to treat a variety of diseases.
6. Identify the problem.
7. What was Fleming's hypothesis?
8. How was the hypothesis tested?
9. Should the hypothesis be supported or rejected based on the experiment?
10. This experiment lead to the development of what major medical advancement?
The Elephant Poem by John Godfrey Saxe (1816-1887)
It was six men of Indostan
To learning much inclined
Who went to see the Elephant
(Though all of them were blind),
That each by observation
Might satisfy his mind
The First approached the Elephant,
And happening to fall
Against his broad and sturdy side,
At once began to bawl:
"God bless me! but the Elephant
Is very like a wall!"
The Second, feeling of the tusk,
Cried, "Ho! what have we here
So very round and smooth and sharp?
To me 'tis mighty clear
This wonder of an Elephant
Is very like a spear!"
The Third apprached the animal,
And happening to take
The squirming trunk within his hands,
Thus boldly up and spake:
"I see," quoth he, "the Elephant
Is very like a snake."
The Fourth reached out an
eager hand,
And felt about the knee.
"What most this wondrous beast is like
Is mighty plain," quoth he;
"Tis Clear enough the Elephant
Is very like a tree."
The Fifth, who chanced to touch the ear,
Said: "E'en the blindest man
Can tell what this resembles most;
Deny the fact who can,
This marvel of an Elephant
Is very like a fan!"
The Sixth no sooner had begun
About the beast to grope,
Then seizing on the swinging tail
That fell within his scope,
"I see," quoth he, "the Elephant
Is very like a rope."
And so these men of Indostan
Disputed loud and long.
Each in his own opinion
Exceeding stiff and strong,
Though each was partly in the right,
And all were in the wrong
Literature and the Scientific Method
1. How does this poem illustrate the importance of observation in the scientific method?
2. What is the moral of the tale?
3. Many scientific errors can occur because the researcher does not use good skills of observation.
Imagine a scenario where not being observant can result in an experiment going wrong. Describe this
scenario in the form of a story or a poem.
Independent and Dependent (Responding)
Variables
Scenario
1. One cow is fed a growth hormone and
another cow is not. After a year, both cows are
weighed.
2. Mosquito repellent is sprayed on one arm and
the other arm is not sprayed. The number of
mosquito bites is counted after 2 hours.
3. Bob studies for a test and Jackie does not
study. After the test, they compare their scores.
4. Two cars are on a track and accelerate to 60
mph. At a certain point, both cars slam on the
brakes. The distance it takes for each car to stop
is then measured.
5. A group of people take a diet pill. After 3
months, they measure the amount of weight
they lost.
6. Ants are placed in a tray that is shaped like a
T, at the end of the T, the ants can either go to a
darkened area or a light area. Students count
how many ants end up on the dark side and how
many end up on the light side.
7. One company states that it makes the best
staplers. To prove it, they use the stapler to
staple a thousand papers and compare it to a
competitor. The competitor’s stapler jammed 3
x whereas their stapler only jammed once.
8. A pediatrician designs baby formula to help
babies gain weight. To show his formula works,
he compares the weights of babies that have
been using the formula to the weights of babies
not on the formula.
Independent
variable
Responding
variable
Scenario
Independent
variable
Responding
variable
9. Cockroaches are exposed to the chemical
dioxin. After 3 hours, 45/100 cockroaches are
dead.
10. New houses are spayed on the outside with
an insulating paint. After a year, researchers
determine how much energy each house used.
Scientific Method - Group Project
Instructions: Give each group or pair one of the scenarios below. Ask the group to design and
experiment to answer the experimental question. Students should identify a control group,
dependent and independent variables and possible outcomes or what type of data would be
gathered. Stress to students that they will not actually be performing these experiments.
Have students either turn in their design on paper or do a mini-presentation to the class.
Does the wavelength of light (R.O.Y.G.B.I.V.) affect a plant’s growth?
Does Rogaine really improve hair growth?
Is acid rain causing a decline of frog populations?
Does the hormone estrogen increase the milk yield of dairy cows?
Does the size of a fish tank determine how large a fish will grow?
Does aspirin keep cut roses fresher longer?
Will crickets chirp more if the temperature is warmer?
Do wounds heal faster when they are covered by Band-Aids?
Which battery lasts longer, energizer or duracell?
Does hot water freeze faster than cold water?
Do tanning beds cause skin cancer?
What causes leaves to fall in autumn (light, temperature, or both)?
* Images obtained from clker.com
Identify the Controls and Variables
Smithers thinks that a special juice will
increase the productivity of workers. He
creates two groups of 50 workers each
and assigns each group the same task
(in this case, they're supposed to staple
a set of papers). Group A is given the
special juice to drink while they work.
Group B is not given the special juice. After an hour,
Smithers counts how many stacks of papers each group has
made. Group A made 1,587 stacks, Group B made 2,113
stacks.
Identify the:
Homer notices that his shower is
covered in a strange green slime. His
friend Barney tells him that coconut
juice will get rid of the green slime.
Homer decides to check this this out by
spraying half of the shower with coconut
juice. He sprays the other half of the
shower with water. After 3 days of
"treatment" there is no change in the
appearance of the green slime on either side of the shower.
6. What was the initial observation?
Bart believes that mice exposed to
radiowaves will become extra strong
(maybe he's been reading too much
Radioactive Man). He decides to perform
this experiment by placing 10 mice near a
radio for 5 hours. He compared these 10
mice to another 10 mice that had not been
exposed. His test consisted of a heavy
block of wood that blocked the mouse
food. he found that 8 out of 10 of the radiowaved mice were
able to push the block away. 7 out of 10 of the other mice
were able to do the same.
Identify the-
Krusty was told that a certain itching powder
was the newest best thing on the market, it
even claims to cause 50% longer lasting
itches. Interested in this product, he buys
the itching powder and compares it to his
usual product. One test subject (A) is
sprinkled with the original itching powder,
and another test subject (B) was sprinkled
with the Experimental itching powder.
Subject A reported having itches for 30 minutes. Subject B
reported to have itches for 45 minutes.
Identify the-
1. Control Group
2. Independent Variable
3. Dependent Variable
4. What should Smithers' conclusion be?
5. How could this experiment be improved?
Identify the7. Control Group
8. Independent Variable
9. Dependent Variable
10. What should Homer's conclusion be? It
doesn't work
11. Control Group
12. Independent Variable
13. Dependent Variable
14. What should Bart's conclusion be?
15. How could Bart's experiment be improved?
16. Control Group
17. Independent Variable
18. Dependent Variable
19. Explain whether the data supports the
advertisements claims about its product. - It
does
Lisa is working on a science project. Her task
is to answer the question: "Does Rogooti
(which is a commercial hair product) affect
the speed of hair growth". Her family is
willing to volunteer for the experiment.
20. Describe how Lisa would perform this
experiment. Identify the control group, and the
independent and dependent variables in your
description.