Transcript Catalyst (4 min) - Schurz High School

Catalyst (4 min)
1.
Why is it important to communicate your
results after you perform a lab
experiment?
2.
What do we do if our results do not
support our hypothesis?
Where are we?

Last week: Observation
 How

Yesterday: Scientific Method
 How

we collect data in the lab
we solve problems in the lab
Today: Experiment Design
 How
we design a procedure to solve
problems
Experiment Design
9/21/10
Elements of a good experiment
Beriberi
 Scientists thought
bacteria caused Beriberi
 Injected a group of
chickens with bacteria
 Left one group of
chickens alone
 Observed which
chickens got sick
Control
 Independent
Variable
 Dependent
Variable

Independent Variable
A change caused
by the scientist
Beriberi
 Scientists thought
bacteria caused Beriberi
 Injected a group of
chickens with bacteria
 Left one group of
chickens alone
 Observed which
chickens got sick
Dependent Variable
A variable whose
value depends
upon the
independent
variable
 What we observe
in the lab

Beriberi
 Scientists thought
bacteria caused Beriberi
 Injected a group of
chickens with bacteria
 Left one group of
chickens alone
 Observed which
chickens got sick
Control
The standard that
is used for
comparison
Beriberi
 Scientists thought
bacteria caused Beriberi
 Injected a group of
chickens with bacteria
 Left one group of
chickens alone
 Observed which
chickens got sick
Constant


Something that is
held the same
throughout the
experiment
In order to make
sure we know
exactly what’s
causing a change,
we can only alter
one variable at a
time!
Examples
 The number of chickens
 The amount of bacteria
injected
 What all of the chickens
ate