Transcript Graphing / Variables / Theories / Laws

Graphing / Variables
/ Theories / Laws
A
A
B
A
D
A
E
A
G
A
H
A
C
A
F
A
I
A
Which
graph
shows
exponential
growth
(quick
then slow
Which
graph
stays
constant
(no
change)?
Which
graph
has
no
correlation?
Which
graph(s)
show
a
decrease?
Which
graph(s)
show
an
increase?
increase)?
Compare and Contrast
Theory / Law
• Scientific theories are systematic sets of concepts that offer
explanations for observed patterns in nature. Theories provide
frameworks for relating data and guiding future research.
Theories may change as new data become available. Any valid
scientific theory has passed tests designed to invalidate it.
• Scientific laws are generalizations of observational data that
describe patterns and relationships. Laws may change as new
data become available.
The Nature of Scientific
Investigations
Experimentation
Methods of Scientists
– A hypothesis is tested by conducting an experiment,
which is an organized procedure that involves making
measurements and observations.
– A good scientific experiment tests only one variable, or
changeable factor, at a time.
• The independent variable in an experiment is the
factor that is manipulated by the experimenter.
• A dependent variable is a factor that can change if
the independent variable is changed.
– A control is used to show that the results of an
experiment are a result of the condition being tested.
Methods of Scientists
Section Assessment
1. Match the following terms with their definitions.
D hypothesis
___
A. factor in an experiment that can
change if the factor that is
B independent variable
___
manipulated by the experimenter
A
___ dependent variable
is changed
C
___ control
B. factor that is manipulated by the
experimenter in an experiment
C. standard for comparison in an
experiment
D. suggested explanation for an
observation often stated in the
form of a question that can be
answered by the results of an
experiment
Practice • Identify IV DV Control in experiments – using the text - P25 #20-23
• 20. Explain how you might test which of three paper towels is
most absorbent.
Measure three equal volumes
of water and pour them onto
a surface, then apply three
differentthe
paper
towels
of amount of
• 21. Suppose you were testing
effects
of the
equal tall
areagrass.
to absorb
the
fertilizer needed to produce
What
would be your
waterdependent
and measure
the time Your control?
independent variable? Your
variable?
required for eachindependent
towel to variables:
amount and type of fertilizer;
absorb the water.
dependent variable: height of
grass after a specified time;
control: grass to which no
fertilizer was applied
Practice
• 22. A doctor is testing a new cancer drug. She chooses 50
patients who have the particular cancer to take part in the
study. She gives 25 patients the new drug and the other 25
patients a placebo, which is a substance that contains no
active ingredients. What is the purpose of this second group in
the doctor’s study?
The second group was the
control.
Several groups
• 23. Suppose you want to find out whether doubling
the of plants
would
beof
grown
under the
amount of potassium in a soil will increase the
yield
tomato
same conditions; only the
plants. Describe how you would test this hypothesis.
What
amount of potassium would
would be your variables? What would you use
as a control?
change—the
independent
variable. The dependent variable
would be the yield of the
plants; the control would be
plants to which no potassium
was added.
Compare and Contrast
Theory / Law
Theory
Law