Topic: Scientific Method
Aim: Explain how a controlled experiment is
performed.
Do Now:
1. Take out your lab safety activity.
2. Tape the Experimental Variables reading
on the first piece of paper in your ISA
section. Write the answers on the looseleaf below.
HW: Complete Part 2 of Lab Safety Activity.
Let’s summarize…
Identify the improper lab procedure observed in
the diagram.
Let’s review…Identify the improper lab
procedure observed in the diagram.
Identify the
ONE factor
that is
difference
between all
three flower
pots.
Amount of
water
Variable
• The ONE factor between all setups that is DIFFERENT
Does fertilizer X help plant
growth?
Group A
Group B
Identify the
variable in
this
experiment.
Control Group
Experimental Group
Parts of a controlled
experiment
• 2 groups:
1.Experimental group: has the
VARIABLE
2.Control group: DOES NOT have
the variable
Control Group
Group A
Experimental
Group
Group B
Explain why group B is the
experimental group.
2 types of variables
1. Independent Variable:
the 1 factor that is DIFFERENT
between groups
Independent variable = ?
SUNLIGHT
2. Dependent Variable = what is
MEASURED (data)
HEIGHT
Topic: Scientific Method
Aim: Explain how a controlled experiment is
performed.
Do Now:
1. Take out your lab safety activity.
2. Make sure your 3 binder sections are set
up: Class Notes, ISA, Homework
HW: Finish Lab Safety Activity.
Let’s summarize…
Identify the improper lab procedure observed in
the diagram.
Height = 12 cm
Height = 21 cm
1. Identify the
independent
variable.
Amount of water
2. Identify the
dependent
variable.
Width of pedals
Group A
Group B
How many indep. variables?
• ONE
• Everything else must be kept
the same  CONTROLS or
CONSTANTS
To make the results of an
experiment more
RELIABLE/VALID/RELIABLE
• Repeat experiment
• Use a larger sample size
Let’s summarize…
1. Explain the difference between the control and
experimental groups.
Control group does not have the independent variable. The
experimental group DOES HAVE the independent variable.
2. Explain the difference between the independent
and dependent variables.
The indep. variable is the one factor between set-ups that
changes. The dep. variable is what is measured.
3. How can the results of an experiment be more
accurate?
Repeat the experiment. Use a larger sample size.
Experiment
1. Identify the independent variable. Color of light
2.Identify the dependent variable. Plant height
3.Explain the difference
between the control
group and experimental
groups in this experiment.
The group with white
light (sunlight) is the
control group. Plants
under different color
lights are the exp.
groups.
An investigation was done with an
electromagnetic system made from a
battery and wire wrapped around a nail.
Different sizes of nails were used. The
number of paper clips the electromagnet
could pick up was measured.
Independent variable:
• Sizes of nails
• These were changed by the
scientist
Dependent variable:
• Number of paper clips picked up
Let’s review…
Identify the improper lab procedure observed in
the diagram.
Let’s summarize…
Identify the improper lab procedure observed in
the diagram.
The set-up that has the
independent variable is
known as the
a. independent variable
b. control group
c. dependent variable
d. experimental group
What is the factor that
changes between all set-ups
of an investigation?
a. Control
b. Independent variable
c. Hypothesis
d. Dependent variable
During an investigation, what
is being measured is called
the
a. control group
b. independent variable
c. controls
d. dependent variable
What is the factor in an
experiment that remains
constant or the same?
a. Control
b. Variable
c. Theory
d. Hypothesis
The set-up that does not have
independent variable is
known as the
a. independent variable
b. control group
c. dependent variable
d. experimental variable
The results of one experiment carried
out by a research team would be
considered VALID if
a. the experiment had no control setup
b. all the members of the research team
came to the same conclusion
c. the experiment had more than one
variable
d. the experiment was repeated and the
same results were obtained each time
Which statement is true about the
experimental group(s) in an
experiment?
1. It does not contain the independent
variable.
2. It contains 2 variables.
3. It contains the independent variable.
4. It is exactly the same as the control
group.
To investigate how temperature affects seed
germination, a student placed 10 radish
seeds of the same variety on moist paper in
each of 3 petri dishes and placed the dishes
in the following environments:
Dish # 1: Refrigerator, 5ºC
Dish # 2: Room Temperature, 20ºC
Dish # 3: Incubator, 37ºC
1.Identify the independent variable in this
investigation.
Temperature
To investigate how temperature affects seed germination,
a student placed 10 radish seeds of the same variety
on moist paper in each of 3 petri dishes and placed the
dishes in the following environments:
Dish # 1: Refrigerator, 5ºC
Dish # 2: Room Temperature, 20ºC
Dish # 3: Incubator, 37ºC
2. Identify the control group.
The seeds in room temperature
3. Identify the dependent variable.
How many seeds germinated
A student wanted to perform an
experiment to test the effect of
water temperature on the time it
takes an egg to boil. He thinks that
the higher the temperature of
water, the faster an egg will boil.
• Independent variable?
temperature of water
• Dependent variable?
time to cook an egg
Beta-carotene supplements have been thought to
protect against cancer. A study was conducted
with 39,000 women aged 45 and up. Group A
received a beta-carotene supplement. Group B
received a placebo. Their health was studied
over their lifetime. Cancer rates for women
taking the beta-carotene supplement did not
really differ from the cancer rates of those
women taking the placebo.
Identify the independent variable, dependent
variable, control group, and experimental
group.
• Independent variable:
Beta-carotene supplement
• Dependent variable:
Their health
• Control group:
Group that received the
placebo
• Experimental group:
Group that received the
supplement
Ex # 2: To investigate the effect of a substance on plant
growth, 2 bean plants of the same species were grown
under identical conditions with Substance Z added to the
soil of one of the plants. At the end of 2 weeks, the plant
grown with Substance Z was 12.5 cm tall. The plant
grown without Substance Z was 12.2cm tall. The
researcher concluded that the presence of Substance Z
causes the plants to grow taller.
What is the independent variable?
Substance Z
What is the dependent variable? height
Which setup is the control?
Plant without Substance Z
Ex #3: A student placed 5 geranium plants
of equal size in 5 environmental chambers.
Growing conditions were the same for each
plant except for the amount of water each
received. At the end of 20 days, the width of
the leaves was measured.
What is the independent variable?
What is the dependent variable?
Which setup is the experimental group?
5. An investigation was designed to determine
the effect of ultraviolet light on mold spore
growth. Two groups of mold spores were
grown under identical conditions, except
one group was exposed only to ultraviolet
light, while the other group was grown in
total darkness. In this investigation, the
group of mold spores grown without
receiving any ultraviolet light is known as
the
a. experimental variable
b. hypothesis
c. control
d. limiting factor