Tips for a Good Scientific
Make sure the tested variable is the only
thing that varies.
For example, if you want to test what effect Miracle
has on plant height, make sure that the amount of Miracle Gro is the
thing that is different among all of your trials. If you put half
the plants by the window and the other half on your dresser in a dark
of the room, you have not isolated the variable you are testing.
amount of sunlight is another factor that varies among your
and invalidates your results.
Choose the best and most
precise instruments possible for making exact measurements.
We've seen in class that beakers are good
for a rough approximate measure of volume, but they are not very good
accuracy. When making a measurement, decide if the measurement
to be exact and remember:
- Look at the markings on the instruments. The
instrument with the smallest interval between markings will be more
- If two instruments have the same intervals marked, choose
"skinnier". Most often, this will be the more accurate instrument
there will be a larger distance between markings. This enables it
be read with a higher precision.
Make sure you are using the
best sample size
Use a sample size that is appropriate
for the instrument that you are using to measure it. If you are
a sample that is about as small as the smallest markings on the
(or smaller), than you are measuring something beyond what the
is designed to measure. Either choose a larger sample size or a
Make sure your sample is a
true representative of the tested item.
For example, if you are testing
the amount dissolved oxygen in a pond, do not just take samples from
top layer of water. Be sure to take samples from all different layers
the pond. The top layer will always have a higher oxygen level,
if that is all you are sampling, your results will not show an accurate
of the pond as a whole.
Also, be sure to take your samples from different regions of the pond.
is possible you might be taking your samples by a drain inlet where
water from a nearby stream is entering the pond. This water will
much higher in oxygen, and if you only take your samples from this
will not be a true representation of the water in the pond.
Perform multiple trials and
average together for Experimental Answer.
Any experiment should exhibit
good precision to ensure its reliability. This means that the
should be repeatable. The golden rule is to always perform at
three trials to verify your results. If you do not get similar results
all three trials, more trials should be done. If possible, it is
a good idea to try to vary your sample size in each of your trials.
To determine your experimental answer, take the average of all of your
Do not simply choose one trial that looks or feels right. The
information from each trial is sacred and should not be ignored or
Trust your Data. Do
not "fudge" or throw away data just because it looks or feels wrong.
As mentioned above, the data
collected during experimentation is sacred and should not be
changed, or discarded because it doesn't look or feel right.
a trial result does appear to be quite different from all of the other
results, you may perform the Q-Test
to see if the data is an anomaly and can statistically be discarded.
However, if a "Blunder" (spilled some of the sample, etc.) is made
the trial the results will obviously be invalid and therefore discarded.