2. Goal
This study and experiment is
attempting to conclude
whether Crest toothpaste
can prevent cavities.
3. Subjects of Experiment
• Population
The population of interest consists of people
who suffer from cavities.
• Subjects
In a dentist office, patients are subjectively
categorized based on their dental records of how
many cavities they have had prior to the
experiment (many, few, very little). Then they are
labeled according to the number of members in
each group. The subjects are randomly picked
using the random number table. 50 are randomly
picked from each group. The total number of
subjects is 150.
4. Explanatory Variable
Type of Toothpaste
The factor is the type of
toothpaste that is
assigned to the patient,
which is Crest or a
generic brand.
5. Treatment
Treatment One
Brushing twice a
day with Crest for
1.5 minutes using a
dime-sized amount
Treatment Two
Brushing twice a
day with a generic
toothpaste for 1.5
minutes using a
dime-sized amount
Experimental Group
Those with low,
moderate, or high
cavity numbers
receiving the
treatment using
Crest toothpaste
Control Group
Those with low,
moderate, or high
cavity number
6. Experimental Design
Explanation
In this experiment, a local dentist office will be selected. Patient records will
be sorted into three major categories – those with low, medium, and high
number of cavities prior to the experiment. Depending on the number of people
in each category (though there are more than 50), each person will be
correspondingly labeled with a number. A random number table will be used to
pick 50 distinct numbers, which correlate in the end to 50 chosen participants
from each cavity category. The 50 in each of the three groups will be put into
pairs depending on the number of cavities each has had, trying to be as exact in
prior cavity numbers as possible. From there, each participant will be required to
eat a specific amount of sweets a day – two chocolates and one lollipop. Within
each pair, one will be given a tube of generic toothpaste and the other a Colgate
tube by random assignment using a random number generator. Both will use a
dime-size of their toothpaste in the morning (between 5-9am) and evening
(between 8-12am) for precisely 1.5 minutes. After six months, the teeth of the
subjects will be thoroughly examined for any possible cavities or any signs of a
developing cavity. Neither the subjects nor the dentists will know what brand is
given to each participant in order to double-blind the experiment and keep
results objective.
7. Experimental Design
Diagram
Group 1,
Low-Cavity History:
50 subjects
150
subjects
Group 2,
Medium-Cavity
History:
50 subjects
Group 3,
High-Cavity
History: 50
subjects
25 pairs
according to
exact # of cavities
previously had
25 pairs according
to exact # of
cavities previously
had
25 pairs according
to exact # of
cavities previously
had
1st person in
each pair gets
Colgate
2nd person
in each pair
gets Colgate
1st person in
each pair gets
Colgate
2nd person
in each pair
gets Colgate
1st person
in each pair
gets
Colgate
2nd person
in each pair
gets Colgate
Random Assignment
Cavity
Prevention
within each
pair
Cavity
Prevention
within each
pair
Cavity
Prevention
within each
pair
8. Control-
The patients assigned the Colgate
toothpaste are the control, and it provides a
base for comparison
RandomizationReplication-
The patients are randomly picked
from the three cavity history
groups. Randomization is also used
to assign one person in each pair
one of the two toothpastes
The study is done over a period of 6
months. This same experiment will
be repeated with the same process
after the 6 months are over with
different patients from a different
dentist office
9. Blocking
Blocking is used in the experiment
The patients are blocked into groups depending on how prone they
are to getting cavities (People who have gotten many cavities 5-6,
moderate cavities 3-4, and very few cavities 0-2
This blocking is used to see the effect of Crest toothpaste on various
levels. It tests the Crest’s ability to prevent cavities on teeth that are
more prone to cavities and have had more damage or those that are
less prone to cavities and have had less damage.
10. Blinding
Double Blinding is used in the experiment
The patients have been paired into two by the number of cavities
they have previously had. One person in the pair will receive the
Crest and one will receive the generic brand.
They will not know which toothpaste they are receiving in order
to avoid bias. If they know they are getting Crest they may use it
more diligently while the ones who know they are getting the
generic brand may not.
The observer will not know which toothpaste is used on which
patient as well, so he can make objective observations once the
treatment is over.
11. Placebo
A Placebo is not required in this experiment because
we are not testing the impact of one thing, but are
comparing the effect of one toothpaste against
another. A placebo would not make sense because
we need to see how much more prevention is
provided by Crest compared to a generic brand of
toothpaste.
12. Potential Concerns
Food Intake
Depending on the person, daily food and sugar intake can
potentially affect the results, as sugar and certain foods can
increase the chances of cavity development.
Brushing Habits
It is impossible to monitor every subject to check whether or not
they are brushing every morning and evening and for the specific
amount of time, so the experiment can be impacted by potential
subjects that do not follow the guidelines.
