Name:
Hour:
Date:
Would you fall for that?
Would you fall for the placebo effect? Watch this video, then complete the rest of the questions.
¥t¥d
1. Why do you think the people in the video got stronger?
the drink made them stronger
thought
They
were and tried harder
so maybe they believed they
*
.
Similar to the video, Mrs. Gallas wants to use a beverage to test the affect that caffeine can have on
heart rate. Here is an initial plan:
• measure initial pulse rate
• give each student some caffeine (Coca-Cola)
• wait for a specified time
• measure final pulse rate
• compare final and initial rates
2. What are some problems with this plan? What other variables will be sources of variability in
pulse rates?
•
•
nothing
There is
maybe sugar
•
people
know
could
be
increases
they
in
to
compare the results
pulse
their heads
.
.
rate, not caffeine
drinking
are
to →
caffeine
.
so it
Control
Group
control
for other
→
variables
( placebo effect)
→
3. Go back up to your list in #2 and propose a solution to each problem.
Blinding
4. Design an experiment to test the effect that caffeine has on heart rate.
Take the students
into
qg§
2
groups
.
and
Give
one
caffeine free
and the other group
in their
the change
Compare
&
'
-
's
created
coke
heart rates
9YY¥dents
y
*EEF3%naen+s→ tfsasigdnmment
s
split them
randy
group regular coke
→
.
.
Treatment I
caffeine
roughly
↳ Compare
change
in
agiiip%9Eereatmentat.mg#
the students
caffeine
free
control Group
Name:
Hour:
Date:
Designing Experiments
.FI#EngiFmeIEisn&oneast:is igna/.E
IT # I
•
Control group used to
:
provide
are unaware
is
LT# 3 4 key principles of
Experiments
besides treatments constant
of
given
Placebo Effect : when
④ Replication
°
a
to
:
using
distinguish
treatment (placebo
) Your Understanding:
Check
works
.
:*.im?EesiEaEeoFa:::am.en;
What treatment
fate
② Randomize ③ Assign
-
baseline data
who interact
•
Conducting random Assignment
it# 2
① Label
Important Ideas:
enough
.
exp Uh It's
.
differences
.
.
A group of researchers in Africa find a creative way to protect cattle from lion attacks – they paint eyes on
the cows’ rears. To determine if this treatment is effective, they randomly assign the cattle to one of three
treatments: Eyes on their rear, cross-marks on their rear, or nothing on their rear. After 4 years of roaming
the plains, the cows with eyes saw no deaths, the cows with a cross suffered 4 deaths, and the cows with
no marks suffered 15 deaths.
a. Explain why it was important to have a control group that didn’t get a mark on their rear.
A control
baseline data so we have
group provides
treatment
to compare to It shows how many deaths w/ no
something
.
b. Suppose the researchers had 1200 cows. Describe how to randomly assign the cows to the treatments.
Label the cows from 1 to 1200 Use RNG i , 1200 to select
(
.
400 unique # s Assign the
Repeat the process
cows
corresponding
to select 400
'
.
eyes
them
.
to
get
the
crosses
All
.
more
remaining
cows
)
to
get the
cows
get
.
no
Assign
marks
c. What is the purpose of randomly assigning treatments in this context?
roughly equivalent
assignment creates
out other variables like
groups by balancing
size
Random
cow
.
d. Create an outline showing a completely randomized design for the experiment.
1200 cows
f.
Assignment\
Random
→
→
Treatment I
Gurfnopdans
→
Group &
Treatment
→
400 Cavs
Guyonpaws
Eyes
2
crosses
-
treatment?
\
-
I
compare
number
deaths
of
.