Completely Randomized versus Matched Pairs Experiment
Comparing Hand Strength: Is the right hand generally stronger than the left in
right-handed people? You can crudely measure hand strength by placing a
bathroom scale on a shelf with the end protruding, then squeezing the scale
between the thumb below and the four fingers above it. The reading of the scale
shows the force exerted.” [BPS/page 198/problem 3.43]
1. Diagram a completely randomized experiment to compare the strength of the
right and left hands, using 10 right-handed people as subjects.
2. Diagram a matched pairs experiment to compare the strength of the right and
left hands, using 10 right-handed people as subjects.
3. Which of the two designs is appropriate? Why.
Completely Randomized Experiment
R
a
n
d
o
m
Available
group of
patients (10)
Available
group of
patients (10)
A
s
s
i
g
n
m
e
n
t
R
a
n
d
o
m
A
s
s
i
g
n
m
e
n
t
Group 1
(5)
Group 2
(5)
Measure left hand
Measure right
hand
Average
left hand
measures
Average
right hand
measures
Compare
averages
Match Pairs Experiment
Group 1
(5)
Group 2
(5)
Measure left hand
first, then
right hand
sesecond
Measure right
hand first, then
left hand
For each
subject,
subtract right
hand from left
hand and take
average of that
list of numbers
Compare
to zero