ap biology. science a way of learning about the natural world includes all of the knowledge gained...
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Introduction to Experimental Design
AP Biology
ScienceA way of learning
about the natural worldIncludes all of the
knowledge gained by exploring the natural world
This knowledge is always growing and changing as scientists ask new questions and explore new ideas
Scientific InquiryScientific: Of or relating to the practice of
scienceInquiry: A close examination of a matter in a
search for information or truthScientific Inquiry: The ways in which
scientists explore the natural world
How Does Scientific InquiryWork?Scientific Method:
Make observations and/or inferences
Ask questionsDevelop hypothesesDesign experimentsMake measurementsCollect dataInterpret dataDraw conclusionsCommunicate
Make Observations and InferencesObservation: Using one or more of your
senses to collect dataInference: An interpretation of an
observation that is based on evidence or prior knowledge
Data: Facts, figures and other evidence gathered through observation
QuestionYou ask a question
about what you observe.
State the problem or question. Example: Does the
drop height affect the bounce height of a superball?
Developing a HypothesisHypothesis: A possible explanation for a set
of observations or answer to a scientific question
A hypothesis must be something that can be tested
Worded as an If . . . Then statementHypotheses can either be supported or
disprovedExample: If a superball is dropped from
increasing heights then the bounce heights will also increase because…
Null HypothesisA hypothesis that can be rejected-it
essentially states that the variables will have no effect on the outcome of the experiment
Why use a Null Hypothesis?You can never have enough support for a
hypothesis to say that it is the sole explanation of a phenomenon, but you can have enough data to show that it is not the sole explanation of a phenomenon.
Designing an experiment totest a hypothesisAfter you state your hypothesis, you must
design an experiment to test it.You figure out a way to test whether the
hypothesis is supported. Control group– nothing changed Experimental group – one variable
changedThe outcome must be measurable
(quantifiable).Record and analyze data.
Designing a Controlled Experiment.An experiment in which all of the variables
except for one are remain the sameAn experiment that is designed to compare
an experimental group with a control group.Ideally, a control group and an experimental
group differ in only one variable.Control group serves as a comparison to
measure against
Experiment VariablesVariable: Factors that can change in an
experimentManipulated (Independent) Variable: The
variable that is changed during the experiment
Responding (Dependent) Variable: The factor that changes because of the manipulated variableVariable that is measured in the experiment
VariablesIndependent variable
Example: Does the drop height affect the bounce height of a superball? We know the drop heights we will use.
Dependent variableExample: Does the drop height affect the
bounce height of a superball? We don’t know the bounce height before we start.
It is what is being measured.
ConstantsConstant: a variable that does not change
for the duration of an experiment; a value that remains the sameExamples: Does the drop height affect the
bounce height of a superball? The superball does not change during the
experiment. The same force is applied during each trial.
Interpreting DataYou do the experiment using
the method you came up with and record the results.
After the data are collected, they must be organized and interpreted Create data tables,
graphs to represent dataPerform calculations that
will determine what results mean (averages, percentages, totals)
Identify possible sources of errors
Drawing ConclusionsAfter you have
organized and interpreted your data, you must draw a conclusion.
You need to decide if the data support your original hypothesis.
RetestIn order to verify the results, experiments
must be retested.
Communicating
Scientists must communicate their findings to other scientists.
This contributes to the growth of the body ofscientific knowledge.
Scientific Theories
Scientific Theory: A well-tested concept that explains a wide range of observations.
A theory is based on thousands of experiments done by different scientists. A theory is much broader in scope than a
hypothesis. Theories only become widely accepted in science
if they are supported by an accumulation of extensive and varied evidence.
Future testing may prove a theory to be incorrect.