Transcript Slide 1

The Scientific Method
• there’s no single method to
answering questions or solving
problems.
• However, there is one
characteristic of scientific
problem solving: the logical &
organized approach that’s taken:
The Scientific Method
1. Define the problem
2. Form a hypothesis
3. Design an *experiment to
test the hypothesis
4. Conclusion
5. Theory
1. State the problem or objective – This is a
statement of the problem or what you
would like to know about something
2. Hypothesis – A hypothesis is a statement
that predicts what you think will happen
when you perform an experiment based on
the information that you have gathered.
3. Controlled Experiment – isolates one
variable and tests its effects on another.
• A variable is any factor or condition present
in the experiment.
Experimental group – the group in which the
variable is tested.
a) Independent variable – the variable being
tested (cause) It’s the variable that is isolated
and changed in a controlled way monitoring
to see if it causes an effect on a second
variable- the dependent variable
b) Dependent variable – the variable being
observed for change (effect)
c) Constants - all other variables present in the
experiment that remain the same throughout
the experiment. Eg: same plants, soil, temp.
• Control group – group with the independent variable
absent.
• This group is usually the "normal" conditions group
used as a baseline to calculate the actual effect of the
independent variable.
Sample size: of both should be = & representative & be
large enough to have reliable data. The larger the size
the more reliable the data
4. Collect Data – The observations gathered are recorded.
Must be measurable. (tables and drawings)
5. Conclusion – The conclusion is a statement, based on
the data, stating if the hypothesis was proven correct
or not and why.
6. Theory – based upon results of experiment. They
usually hold true ‘till new evidence proves otherwise.
HW: Summary of notes & questions
1. What is the scientific method?
2. What are the steps of the scientific
method?
3. What is the purpose of an experiment?
4. Define:
• Control
• Independent & dependent variable
Scientific Method Wrkshts Answers
The Simpsons and the Scientific Method
The Homer Scenario
• 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 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.
1. What was the initial observation?
• Green slime was growing in the shower
2. Identify the Control Group
• Shower half that was treated with water
3. Identify the Independent Variable
• Liquid/solution used
4. Identify the Dependent Variable
• Growth of the slime
5. What should Homer's conclusion be?
• 3 days of treatment with coconut juice did not
remove the green slime
The Bart Scenario
• Bart believes that mice exposed to microwaves
will become extra strong (maybe he's been
reading too much Radioactive Man). He decides
to perform this experiment by placing 10 mice in
a microwave for 10 seconds. 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 microwaved mice were
able to push the block away. 7 out of 10 of the
non-microwaved mice were able to do the same.
6. Identify the Control Group
• 10 mice not placed in the microwave
7. Identify the Independent Variable
• Use of microwaves or not (exposure to
microwaves)
8. Identify the Dependent Variable
• Number of mice that moved the block of wood
9. What should Bart's conclusion be?
• Microwaves do not give mice extra strength
10. How could Bart's experiment be improved?
• Use another source of energy, repeat the process,
try more mice
The Krusty Scenario
• 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.
11. Identify the Control Group
• Test subject A
12. Identify the Independent Variable
• Type of itching powder
13. Identify the Dependent Variable
• Length of time with itches
14. Explain whether the data supports the
advertisements claims about its product.
• The data supports the claim, but only 2 tests
subjects is not sufficient.
The Lisa Scenario
• 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. Describe how
Lisa would perform this experiment.
15. Identify the control group, the independent,
dependent variables in your description.
15. Identify the control group, the independent,
dependent variables in your description.
• Control: regular hair shampoo
• Rogooti
• Speed of hair growth
Have ½ of her family & friends use regular
shampoo & the other ½ the Rogooti; measure
in cm, the rate of hair growth each week for a
month. See which groups hair grew the
fastest.
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 wholegrain rice, but during the experiment, the chickens were fed
polished rice. Dr. Eijkman researched this interesting case.
he found that polished rice lacked thiamine, a vitamin
necessary for good health.
1. State the Problem
What causes Beriberi?
2. What was the hypothesis?
If the chickens are injected w/a bacteria, then they will
develop beriberi.
3. How was the hypothesis tested?
They injected chickens with bacteria from the blood of
patients with beriberi. The injected chickens became sick
4. Should the hypothesis be supported or rejected based on
the experiment?
Rejected
5. What should be the new hypothesis?
If the chickens are feed polished rice, then they will
develop beriberi.
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.
6. Identify the problem.
What is killing the bacteria?
7. What was Fleming's hypothesis?
Mold must be producing a chemical that killed the
bacteria.
8. How was the hypothesis tested?
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.
9. Should the hypothesis be supported or
rejected based on the experiment?
Yes
10. This experiment lead to the development of
what major medical advancement?
Antibiotics