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Design
Planning the most
appropriate observing programme for the chosen task, including
observing sites, times, instruments needed, and the need for
repeat observations.
Here are the board's criteria for Design
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0
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No procedure designed.
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1
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Outline a simple procedure for the observations, using
basic astronomical terminology.
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2–3
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Astronomical knowledge and understanding used to decide
on the most appropriate site, time, equipment and
observations.
Spelling, punctuation and grammar used with reasonable
accuracy. Limited use of astronomical terminology.
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4–5
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Detailed astronomical knowledge and understanding used to
design the mosts appropriate observing programme with a
range of sites, times and instruments evaluated.
Spelling punctuation and grammar used with considerable
accuracy. Good range of astronomical terminology used
correctly.
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Observation
The record of the range of
observations taken, including any drawings of the objects
observed, details of the observing session (weather conditions,
location, etc.).
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0
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No observations completed.
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1
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Simple observations completed, providing some data.
A few observational details completed.
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2–3
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Sound observations completed and recorded, providing
adequate data for the task.
Clear an accurate observational details included.
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4–5
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Excellent programme of observations completed and
recorded, providing conclusive data for the task.
Full observational details included clearly and
accurately.
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Analysis
The conclusions drawn from the
observational data collected, related to the observational task
chosen.
Here is what the board says about Analysis
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0
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No analysis on the observations
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1
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Simple comments on what is shown by the observations,
using basic astronomical terminology.
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2–3
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Conclusions or calculations derived from observational
data used to address the task set.
Spelling, punctuation and grammar used with reasonable
accuracy. Limited use of astronomical terminology
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4–5
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Full analysis of the observational data, resulting in
clear conclusions relating to the task set.
Spelling punctuation and grammar used with considerable
accuracy. Good range of astronomical terminology used
correctly.
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Evaluation
An evaluation of the data
collected in the observation and suggestions for improvements or
extensions to further observations.
And here is what it says about Evaluation
0
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No evaluation
of the observation
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1
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Simple
comments on the accuracy of the observations, using basic
astronomical terminology. |
| 2–3 |
Supported statement of the accuracy of the observational
data obtained.
Feasible suggestions for improvements or extensions to the
observations.
Spelling, punctuation and grammar used with reasonable
accuracy. Limited use of astronomical terminology
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4–5
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Clearly reasoned quantitative assessment of the accuracy
of the observational data obtained.
Detailed suggestions for improvements or extensions to the
observations.
Spelling punctuation and grammar used with considerable
accuracy. Good range of astronomical terminology used
correctly.
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You will notice that the last paragraphs in each of the 2–3 and 4–5
boxes are the same. The way the assessment works is this
- If simple comments are present, using basic astronomical
terminology, then I award at least 1 mark, and I move on to
consider the 2–3 mark criteria. I don't imagine you will have
any trouble surmounting this hurdle – but note that it requires
comments AND using some astronomical vocabulary.
- If none of the 2–3
mark criteria are satisfied, I revert to the 1 mark already
awarded
- If some of the 2–3
mark criteria are satisfied, but not all, I award 2 marks
- If all of the 2–3
mark criteria are satisfied I award 3 marks, and I move on to
consider the 4–5 mark criteria.
- If none of the 4–5
mark criteria are satisfied, I revert to the 3 marks already
awarded
- If some of the 4–5
mark criteria are satisfied, but not all, I award 4 marks
- If all of the 4–5
mark criteria are satisfied I award 5 marks.
You will notice that this is a completely different approach to
ticking correct things and then adding the ticks up at the end. You
need to tackle the task of writing up with all this in mind. You
have to serve up on a plate to the external examiner precisely where
you have satisfied the criteria. So, for example, you need a heading
"Analysis" and, later, another heading "Evaluation". Within the
"Evaluation" heading, you need an "Accuracy" sub-heading and an
"Improvements & Extensions" sub-heading.
Notes
on Planning
These will follow tomorrow, I hope.
Notes
on Analysis
We are likely to have discussed in some detail how to extract
significant information from your observations. If you follow those
discussions through, you are likely to qualify for the first
paragraph of the 4–5 mark criteria.
To cope with the "good range of astronomical terminology", I
recommend finding the relevant section in the textbook, making a
list of all the words that look as if they might fit the bill, and
then making sure that you incorporate those words into what you
write.
You will start with the sheets of paper that you completed in the
field while taking your observations. This sheet of paper, in its
raw form, will form part of your presentation. You might make
measurements from this sheet, in which case you will put these into
a suitable table, with appropriate headings, etc. If you do this,
you will need to provide a description of precisely what you did to
obtain these measurements, and specify the instruments that you
used. You will probably use these figures to calculate something.
You will need to provide an outline of the theory of what it is that
you are calculating - notes on this website might point you in the
right direction - but what you write has to be in your own words.
Notes
on
Evaluation - 1st sentence
Suppose you are measuring the speed at which a friend is able to
run. You set out a track for them to cover, and then you time how
long it takes them to run that distance. You do this six times,
obtaining the results:
10 s, 11 s, 10 s, 9 s, 11 s, 12 s. The average (technical word: mean)
of these times is 10.5 s, and you want to give an indication of the
spread, or how close to each other the readings are. The easiest
thing to do is to notice that the difference between the highest and
lowest is 3s, and that they lie 1.5 s away from the mean. The 1.5 s
is called the uncertainty.
So you could say
mean time to run the course = 10.5
s ± 1.5 s
Rather better is to express the uncertainty as a percentage of the
mean, which you do by dividing the mean into the uncertainty and
multiplying by 100. In this case it comes out at a little over 14%,
so you would say
mean time to run the course = 10.5
s ± 14%
Whenever you end up with several
versions of a reading that ought to be the same, you should
calculate a mean and percentage uncertainty. It may seem
complicated, but that is what the word "quantitative" means in the
first sentence of the Evaluation criteria for 4–5.
In order to find your friend's speed, you need to know how far they
ran, and then divide the time into that distance. So you might both
pace the course out, and come up with the (different) answers 85 m
and 81 m. Proceeding as before, you would calculate
mean distance run = 83 m ± 2.4%
[Make sure you can do this calculation and that you agree with this
answer]
Now it's time to calculate the final result. So we say that the
speed is the mean distance run divided by the mean time taken, which
comes out at 7.9 m/s. [Ensure that you agree with this.] But before
we can give the answer to a startled world, we need to be able to
say how reliable the answer is. So we add the percentage
uncertainties of the distance and time, which comes to about 16%.
Lastly we work out what 16% of 7.9 is (it comes out at around 1.3 –
check this), so that we say, finally:
Our friend's speed is 7.9 m/s ±
1.3 m/s
and we confidently expect that the examiner will remain focused on
the 4–5 box! If you read the first sentence in each of the three
boxes in the Evaluation table, you will appreciate why you have to
go the whole hog.
Notes
on Evaluation - 2nd sentence
This is both easier and harder to deal with. Here are some thoughts:
- It might be that, while you were analysing your readings, you
found yourself saying something like, "I wish I'd taken more
care with this or that aspect of recording the data". If so,
then that will give you an obvious way of suggesting
improvements. But beware of just saying "Take more care". You
have to specify just what you would have done differently which
would have resulted in 'better' readings.
- It is always possible to improve matters by taking more
readings. In the notes above, we have arrived at our percentage
uncertainties by an extremely crude method. What we should
do is to calculate what is called the standard
deviation and then divide by the square root of the
number of readings to arrive at what is called the standard
error. It should be reasonably obvious that if you have
a larger number of readings, then the standard deviation would
then be divided by a larger number, which would make the
standard error smaller. If our percentage uncertainty is
smaller, then we have a more reliable result. Job done.
- Some projects offer several different ways of dealing with
observations. If several approaches are possible, and you have
opted for approach A, then explaining how approaches B and C
would work can be a sensible thing to do, outlining both the new
methods of analysis and the changes in observational procedure
that would have been necessary.
- Suppose that you are doing a physics experiment in which you
are measuring a resistance with the formula voltage/current. You
take several readings of voltage and current, and for each you
work out the resistance. Then you work out the mean and
percentage uncertainty as explained above. An alternative
approach would be to plot a graph of voltage against current,
draw the best-fit line and then take the gradient. Then you can
draw the steepest and shallowest straight lines that your data
points will let you get away with, find their gradients, and use
those to generate a percentage uncertainty of the gradient. So
you could explain that alternative procedure without actually
carrying it out.
- Very often, the quality of observations could be improved by
using a telescope and/or camera. Then you can enlarge
photographs, take careful measurements (which are much easier on
a photograph in a warm brightly-lit room later on than out in
the field in the cold darkness!). Of course, if it was an
unaided project, you wouldn't have been allowed
to do this – but that doesn't invalidate it as a suggestion for
improving the observations in an ideal world.
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