"Basic Statistics for R&D", a
report written by Dr. Jay Apt, has been graciously provided
in PDF form by Bill Spadafora of NARTS.
It is useful in conjunction with Joyce
Guzik's article.
The following article was written for the March/April 2004
issue of Sport Rocketry Magazine (copyright 2004). It is
used with permission.
R&D Advice
by Joyce Ann Guzik, NAR
37191
Editor's note: Joyce
has judged the R&D event at 13 NARAMs. She is a staff
scientist at Los Alamos National Laboratory and holds a
Ph.D. degree in Astrophysics.
This year at NARAM-50, cash prizes of up to $1000 for
first place are being awarded to B-division winners of the
Research and Development competition. Since the stakes are
high, we thought it would be good to give you an idea of
what the judges are looking for, and conversely, what the
judges have often found lacking about R&D reports, and
also give you some useful tips and advice.
First, it is important to read the rules in the 'Pink
Book' on this event that can be found at
www.nar.org/pinkbook. You must submit three copies of your
R&D report for judging. The rules give a list of
elements that must be included in a report in order to
qualify for the event, such as stating how much it cost to
do your project. You must also submit a separate 250-300
word written summary of the report. You must be prepared to
give an oral presentation before the judges if your project
is in contention for 1st through 4th place.
Getting an idea for a
project
According to the Pink Book, an R&D project is
supposed to either advance the state of the art of model
rocketry, or use model rocketry as a research tool. Follow
your curiosity. A good project has an idea that shows
creativity and originality, is feasible to execute in a
reasonable amount of time, and (sometimes fortuitously)
leads to a result that is useful, or advances everyone's
understanding.
Is there something that has been mysterious, that you
have always wanted to understand? Have you wanted to improve
the performance of your rocket? Is there something that has
always annoyed you about your rocket (misfires, the way your
parachute tangles or won't deploy, red barons, not being
able to find it after launch, the difficulties of altitude
tracking, lack of guidance, safety concerns, etc.) for which
you might have a novel solution? Is there something that you
could use model rocketry for (e.g., taking atmospheric
science data, taking aerial photos for a particular use,
developing a science curriculum to teach some aspect of
physics or math or chemistry, etc.)? For examples of what
R&D projects have been done in the past, you can search
the World Wide Web, NARTS publications, yearly NARAM issues
of Sport Rocketry, and ask other rocketeers.
Start early!
Don't plan on doing your project a few days before NARAM!
The winning R&D projects in the upper divisions often
take months to over a year to complete, with multiple
aspects/parts/approaches. Building your test rockets or
equipments, testing, allowing time for failures and revising
your approach, and getting a statistically significant
amount of quantitative data from experiments and flight
tests (see below) all take time.
Keep a logbook chronicling your progress, ideas, data,
and observations. It will be useful when it comes time to
write your report.
The written report
Be sure that everything listed in Pink Book rule 63.5 is
included in your report. Your entry could be disqualified if
it does not contain all of the required elements in some
form. Include an introduction about why you chose this
project and what was your initial (and sometimes evolving)
objective for the project.
A written summary of your report is also required. This
is not simply a repeat of the introduction, or an
advertisement for the rest of the project-it is a succinct
summary of your objective, a brief statement of the means
you used to meet it (e.g., calculations, flight tests,
engineering tests, or other data gathering), and a statement
of the conclusions and significant results (What did you
learn? Did you meet the objective?). If a reader had time to
read only your summary, what would you want him/her to know
about your project?
Keep a bibliography and list the sources that you used
for reference. Do go to the library (surprisingly, there is
stuff there that isn't on the web!), look at the web, and
ask other experienced modelers. But make sure your writing
is original-DO NOT cut and paste entire paragraphs from
reference sources on the web or from books unless you have a
purpose for them in the context of the report. Material
taken from a source should appear within quotes in your
report, and a reference to the original source should appear
in your bibliography. Even if you paraphrase material, or
put it in your own words, you need to reference the original
source. Also, stick to the point of your project, and do not
include extensive irrelevant information or descriptions.
You will not earn extra credit for padding out your project
with more pages.
Periodically during your preparations, you should try to
step back and think carefully about your experimental setup
and think about what else could account for or affect your
results (was Rocket B heavier than rocket A by a little? Did
Rocket B have slightly crooked fins and so not fly as
straight or have more drag?). Include these thoughts in your
report. Even if you don't know how to correct for such
systematic errors, just doing some thoughtful analysis and
itemizing other possible causes for the results will earn
you the esteem of the judges!
It would also be good after the conclusions in your
report to include a retrospective on what you would do
differently if you could start over, your thoughts on
follow-up work that could be done to improve the project, or
other ideas that this project inspired.
Please have several other people read your report before
you enter it in the R&D event. Have them make
suggestions for improvements. Find out what things they
thought were confusing or missing. Also, be careful to
eliminate all of the grammar and spelling mistakes (a good
proofreader helps here too!).
The significance (or lack thereof) of
your results
One thing that the judges are especially looking for is
that the contestant is not drawing incorrect or unsupported
conclusions from their observations and experimental
results.
This can arise for two reasons. First, the contestant may
not have enough controls or checks in his/her experimental
process. For example, if you are doing a lot of flight tests
with several different models, you need to check for and
record possible differences between the models. Do they have
the same mass, surface finish, fin area, frontal area, etc.?
Also, follow procedures that help to 'randomize' the effect
of influences that you may not consider or can't control.
For example, if you are comparing the performance of A vs. B
engines using what you think are two identical models, don't
fly all of the A engines in one model, and all of the B
engines in the other model; divide the two types of engines
evenly between the models. Similarly, if you are comparing
two different types of models, don't make all the flights of
model #1 in the cool, clam morning, and then make all the
flights of model #2 in the hot, windy afternoon; mix the
flights together so that external changes affect both groups
equally.
The second reason people draw unsupported conclusions is
that they don't consider whether any differences in their
results are statistically significant or not. For any
quantitative data it is a must to have some statistical
analysis. Most importantly, you need to have enough trials
of an experiment to get statistically significant results.
One to three trials is much too few to get significant
results; ten to twenty would be much better. At a minimum,
you should calculate the 'mean' (average) and the 'standard
deviation of the mean' ( )
for all sets of experimental data you want to compare. Note
that
is NOT the standard deviation of the data sample, but the
standard deviation of the mean of the data sample (which is
the standard deviation of the sample divided by the square
root of the number of trials in the sample).
The short technical report Basic Statistics for R&D
by NASA astronaut and rocketeer Dr. Jay Apt, available from
NARTS (www.nar.org/narts), discusses in detail the
calculation of mean and standard deviation of the mean. This
is an estimate of how far your calculated mean is likely to
differ from the true mean that would be found by doing a
very large number of trials. There is a 68% chance that the
true mean lies in the range +/-
on either side of your sample mean; the chance is 95% that
it's in the range +/-2 .
If the
error ranges of two sets of experimental data overlap, then
you cannot claim there is a statistically significant
difference between the two sets. For example, as Dr. Apt
points out, if you have a set of trials of rocket A with an
average altitude 320 +/- 20 meters, and a set of rocket B
with 310 +/- 20 meters, you cannot conclude that rocket A
reaches higher altitudes than rocket B! Including more
trials in a data set gives a narrower error range for
and can result in you being able to determine a
statistically significant difference that fewer trials will
not reveal.
Figure 1. Rocket data example
spreadsheet
Rather than duplicate Dr. Apt's
report by demonstrating how to calculate the mean and
for your data, we show you how to do it in an Excel
spreadsheet (see Figure 1). The bottom of the figure shows
what formulas are in the cells of column B (the same
formulas are copied across into column C). The "track lost"
entry in cell C6 is there to show that the formulas ignore
cells that are blank or contain non-numerical data.
The spreadsheet shows two sets of rocket altitude
measurements and the mean (average) of each set. But is
there a significant difference between the means? Using the
values from row 10, we can see that the error ranges 191.0
+/- 5.2 and 202.0 +/- 4.7 do not overlap, so the data
are significantly different (at least to 'one sigma'-one
standard deviation of the mean). The difference in the
results would be more convincing if the data were different
at the 'two sigma' level (95% confidence) but they are not,
since doubling the error ranges causes them to overlap. By
the way: if the we only had the first three flights in each
set, the results are 191.7 +/- 11.1 and 204.3 +/- 8.0,
which does not show a clear difference between the two sets
since those ranges overlap.
The Student's t-test formula in cell B13 is another
statistical test that Excel can perform. The result shown
tells us that there is only a 13% chance that the two data
sets come from the same population, another indication that
the data are significantly different.
Oral Presentation
In addition to the written report, the contestants that
are in line to place must do an oral presentation in front
of three NARAM R&D judges and a friendly audience of the
interested NARAM attendees, and answer questions following
their talk from the judges and audience. The presentation
can significantly affect the judges' opinions, but remember
that you need to do well enough to impress the judges on the
written report to earn the chance to present the oral in the
first place!
Prepare your oral talk well: Have vugraphs
(transparencies) summarizing your report (proofread them!),
and use large font sizes for the text so people in the back
of the room can see them. If you are using a computer
projector, the same applies-but have transparencies as a
backup. Have some props as well (samples of your rocket,
apparatus, etc.) to show the judges and pass around.
Practice in front of your family and friends two or three
times before coming to NARAM and ask them for their honest
constructive criticism regardless of how much it hurts your
ego!
The R&D rules state that the oral presentation shall
not exceed 15 minutes in length, but the constraints of time
at NARAM usually lead to the judges to request talks with a
length of 5 or 10 minutes, so you should be prepared for
either length. Contestants that go on past the time limit
may be cut off from necessity without finishing. One
viewgraph per minute is a good rule of thumb. You could have
an additional 5 minutes of material in reserve if it turns
out there is time for a longer format. The judges and
audience will not interrupt you with questions during your
presentation, but there will typically be 5 minutes of
questioning after you have finished your talk. Practice
answering questions from your family and friends.
The judges may ask you to demonstrate some aspect of your
project on the field on Friday, so be prepared for this if
you think your project might warrant it.
Good luck-we are hoping to see many outstanding projects
at NARAM!
[end of Joyce's article]
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