Transcript Scientific Method

Scientific Method
S. Burnham
Biology
2009-2010
Scientific Method
Certain methods to obtain knowledge
 Ask questions, make observations,
ascertain explanations
 7 Steps
 Have you ever asked who, what, where,
when, how, or why? That’s the beginning.
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Steps in the Scientific Method
1.
2.
3.
4.
5.
6.
7.
Use observations to identify a problem
Formulate a hypothesis
Construct a procedure (step by step directions)
Conduct your experiment
Collect and analyze data
Draw a conclusion
Repeat
Step 1: Use observations to identify a
problem
Observation
 Raises questions
 Employs one or more of the 5 senses to
perceive objects or events
 Direct (hear a animal call in the wild) or
indirect (examining electricity)
Step 2: Formulating a Hypothesis
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Statement that explains their observations and
can be tested
If testable, evidence can be collected that either
does or does not support the statement
IF (put independent variable here), THEN (put
dependent variable here) statement
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If the virus causes a deadly disease then introducing
that virus into healthy tissue will cause the tissue to
die.
Not all hypotheses are in If, then format.
Independent vs. Dependent
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Independent is manipulated variable (what you change)
Dependent is responding variable (what happens due to the
change)
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REMEMBER:
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D – dependent
R – responding
Y – axis
M – manipulated
I – independent
X – axis
Step 3: Procedure
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Step by step directions that are self
explanatory
Number your steps
Be specific about equipment, amounts, units,
etc… but not wordy
Step 4: Experimenting
 Process of testing a hypothesis by
gathering data under controlled
conditions
Controlled Experiment
 You change one factor or variable
and observe its effect on another while
keeping all other factors the same
or constant
Experimenting cont…
Variable: factors that can be changed
2 types:
1. Dependent/Responding Variable: what is being
measured
ex. Height, growth, amount of oxygen produced,
etc.
2. Independent/Manipulated Variable: what you
change on purpose
ex. Light exposure, food, time, depth, scent, etc.
Experimenting cont…
Constant: variables that stay the same through out the
experiment
ex. Same amount of water in all beakers, same sized
beakers, same plants…
Control: a sample that is treated like the other
experiment groups but the independent variable isn’t
applied (what normally takes place)
ex. You are testing a new drug. One group received
the drug; the other group was a placebo (sugar pill).
The group given the placebo is the control group.
Scenarios
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As a group, analyze the scenarios to come up
with:
What is the question being raised?
 Independent Variable?
 Dependent Variable?
 Control?
 Constant(s)?
 Write a hypothesis based on the scenario.
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Step 5: Collecting and analyzing data
Forms of Data Collection:
1. Measuring
 Quantitative data: data is measured in numbers
 Number of people in a group
 Measurements of a cube
 Duration of an event
2. Sampling
 Using a small part to represent an entire population
 Must be large and random
 Should include as many subjects as possible
Forms of Data Collection cont…
4. Organizing Data
 Data is useless unless its organized
 Data table, graphs, chart, concept map
(appendix A)
Analyzing Data
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Process of determining whether data you
collected is reliable and if it supports your
hypothesis or not
Data can be analyzed in several ways
Statistics to determine a relationship between the
variables
 Compare the data with those obtained in other trials
or studies
 Determine sources of error
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Analyzing Data cont.
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Data analysis shows general or specific trends or
patterns from a graph that you have created from
your data chart or table.
General Trend:
From 1955 to 1995, the total
amount of ozone
decreased from 325 d.u. to
169 d.u. in Antarctica.
Specific Trend:
From1964 to 1966, the total
amount of ozone
increased from 280 d.u. to
320 d.u. in Antarctica.
Step 6: Drawing Conclusions
1.
2.
3.
Create a Model
•
Constructing a representation of an object or process
that shows a relationship among the data
•
Visual, verbal or mathematical
Inferring
•
Conclusion made on the basis of the facts or data
gathered during your experiment
Forming a Theory
•
May be formed after many related hypothesis have been
tested and supported by much experimental data
•
Broad and comprehensive statement that is thought to be
true
Step 7: Repeat!
Make sure the data is accurate (you can
reproduce it)
Precision: how close you are to the
actual number
Ticket out the door
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Individually answer the questions to Dog
Licking its Wound and turn in before
leaving the class today.