Homework:Scientific Method in the
Real World
Find an article or video from
a reputable scientific source
that demonstrates the
application of the scientific
method.
Must be related to some
field of Biology
Scientific inquiry
Experimental Design
In- Scientific Method
 Read the last page of the black box
packet.
 Write each hypothesis and determine
which would be useful for a scientific
investigation.
 Explain each answer.
 Create a general statement about the
characteristics of a useful hypothesis
Thru-Scientific Inquiry
Question
 Based on observations or information
gained from previous research.
 If an experiment can be done or data
can be collected, then a question can be
answered scientifically
Hypothesis
 Potential answer to the question
 Can be in If, Then format or just a
statement
 Only useful if it can be falsified through
experimentation
Variables
 Independent Variable-deliberately varied
during the experiment. Affects the
dependant variable.
 Can often be time.
 May not be directly manipulated by the
investigator, but data can be collected to
evaluate the hypothesis.
 Ex: Are more crimes committed during a
full moon?
Variables
 Dependant Variable- what is measured
during the experiment
 Indicates the effect of the independent
variable
Identify the Variables
 The diversity of algal species is
calculated for a coastal area before and
after an oil spill
 Guinea pigs are kept at different
temperatures for six weeks. Percent
weight gain is recorded.
 A scientist hypothesizes that the adult
weight of a dog is higher when it has
fewer litter mates (brothers and sisters)
as a puppy.
Controlled (standardized)
Variables
 Factors that are kept the same in all
treatments
 Isolates the effect of the independent
variable on the dependant variable.
Controlled Variables
 A scientist wants to determine the effect
of temperature on the amount of chicken
eggs hatched
 What is the IV?
 DV?
 Controlled Variables?
Levels of Treatment
 The values set for the independent
variable
 Treatment levels are varied to obtain a
broad set of data
 Typically based on prior knowledge of
the system.
Control Group
 A treatment in which the independent
variable is either eliminated or is set at a
standard value (room temperature, etc.)
 Results are compared to experimental
treatments
Identify the control group
 A scientist studies the amount of alcohol
produced by yeast when it is incubated
with different types of sugars
 The effect of NutraSweet on tumor
development in lab rats is investigated
 The effect of light intensity on
photosynthesis is measured by collecting
oxygen produced by a plant.
Replications (trials)
 Repeat the experiment several times
using the exact same conditions.
 Determines consistent results
 Don’t expect the exact same result in
each replication. A certain amount of
variation is expected in biological
systems.
 Be sure your sample size is not too small
Out- Experimental Design
 A group of students hypothesizes that
the amount of alcohol produced in
fermentation depends on the amount of
glucose supplied to the yeast. They want
to use 5%, 10%, 15%, 20%, 25%, and
30% glucose solutions.



