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Manhã da Carnaval

Posted in Jazz, Music with tags , , on May 7, 2013 by telescoper

I travelled back to Brighton this morning and spent the afternoon in a series of meetings in my sweltering office. I now haven’t got the energy to post anything but some music, so here is some rare footage of Brazilian guitarist and pioneer of Latin Jazz Baden Powell (full name Baden Powell de Aquino) recorded in Germany in 1970. The lovely tune with a melancholy edge is called Manhã da Carnaval. He not only plays it beautifully but also displays admirable dexterity in holding his cigarette in right hand as he does so..

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Bank Holiday in Bute Park

Posted in Uncategorized with tags , , , on May 6, 2013 by telescoper

Well, I’ve done next to nothing today. Just yesterday’s Azed crossword in which I found

All too public ‘diary’ left in the loo (4)

which clues what this is.

I also held my last ever project meeting with Cardiff student; hand-in dates are looming across the country, I suspect.

Other than that, I’ve just been strolling around, and otherwise enjoying, Bute Park in the sunshine along with half the population of Cardiff. It is a pity the Council don’t take better care of the grass, though..

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General Paper

Posted in Education with tags on May 5, 2013 by telescoper

Rummaging through my drawers just now I found the General Paper I took in 1981 to get into Cambridge. I haven’t copied Section A, which involves writing a precis of a rather lengthy article about voting systems, but Sections B and C involve different forms of writing challenge.

I don’t remember which questions I answered, but most of the topics are still interesting and/or controversial enough to be topics for a blog post, at least. Which would you have chosen?

Incidentally, the whole paper was of 3 hours duration and all sections were equally weighted so you would be expected to spend about an hour on each question.

I think we should do much more to encourage science students to develop their writing skills nowadays. I think most present-day physics would find these exercises very difficult, simply because they don’t get enough practice at putting pen to paper (or even fingers to keyboard).

If you are feeling keen, and have an hour to spare, feel free to submit a piece through the comments box!

Time starts now…

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Maurice of Montpelier Terrace

Posted in Uncategorized with tags , , on May 4, 2013 by telescoper

I chanced upon this old picture just now. It was taken in Brighton in 1989, and it shows me with Maurice, a gorgeous Burmese cat who was a resident of the basement flat in which I lodged for a while, in Montpelier Terrace. This photograph was taken in the little yard at the rear of the property, from which Maurice frequently tried to escape.

Burmese are wonderful cats, very talkative and full of personality, but their claws are like needles!

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The Joy of Pepys

Posted in Biographical, History with tags , , , , on May 3, 2013 by telescoper

Twitter is much maligned by those who don’t use it, and I’d be the first to admit that it has several million downsides, but every now and again you come across something truly wonderful which makes it worthwhile putting up with the dross. Here’s an example. Some time ago, a nameless genius came up with the idea of tweeting excerpts from the Diaries of Samuel Pepys.  Those of you on Twitter can follow Samuel Pepys by clicking here:

For those of you not familiar with Twitter, its main characteristic is that messages posted on it (“tweets”) are limited to 140 characters. To outsiders this seems to imply that all tweets are banal and pointless, but this is far from the case. The strict length limit forces a form of creativity that is both rare and wonderful. The stroke of genius in this case was to realize that the Pepys Diaries could be tweeted in chunks of the right size, in a manner that almost suggests they were designed for the purpose!

Pepys was a high-ranking naval administrator and Member of Parliament so he had detailed knowledge of the momentous political events of his period. He’s currently tweeting from May 1660 (near the start of the diaries), giving a vivid insight into the background to the Restoration of the Monarchy. Parliament should be recalled in a few days time, on May 8th…

Here is a selection of recent examples:
peps

But it’s not just the fascinating political context that makes these tweets so interesting. They also give glimpses of everyday life in the 17th Century. Pepys was in poor health for much of his life, for example, and there are frequent references to various physicians and their quack remedies. He also manages to conjure up in just a few words the extraordinary atmosphere and energy of the London of the period, along with some of its excesses (especially drinking and fornication).

Following Pepys’ Twitter feed opens a window into 17th Century England, and what comes through it is both refreshing and illuminating. The reason I find this particularly delightful is something that I’ve blogged about before, so won’t repeat at length. I was a very late developer from an education point of view until I was helped with my reading and arithmetic by a wonderful old lady who lived next door. She encouraged me to read and, after a big struggle, I eventually got the hang of it. After a time I had caught up with the rest of the class in School and eventually managed to read just about every book the School had to offer, including the Diaries of Samuel Pepys which were for some reason on the shelves in Class 2 and which I was allowed to borrow. I don’t think anyone had read them before so nobody, including the teachers, knew how rude they were in places. The Restoration period was generally rather bawdy, and Pepys’ Diaries reflect that.

I had no idea at that time, of course, that less than ten years later I would be studying at Magdalene College, Cambridge, site of the Pepys Library where the orignal diaries are kept as well as the rest of Pepys’ own collection of rare books and music.

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Cute Nuclear Physics Problem

Posted in Cute Problems, The Universe and Stuff with tags , , on May 2, 2013 by telescoper

It’s been quite a while since I posted anything in the cute physics problems folder – mostly because the problems I’m generally dealing with these days are neither cute nor related to physics – but here’s one from an old course I used to teach on Nuclear and Particle Physics.

In the following the notation A(a,b)B means the reaction a+A→b+B and the you might want to look here for a definition of what a Q-value is. The Atomic Number of Phosphorus (P) is 15, and that of Silicon (Si) is 14. The question doesn’t require any complicated mathematics, or any knowledge of physics beyond A-level; the rest is up to your little grey cells!

nuclear

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Don’t Leave Me This Way

Posted in Biographical, Music with tags , on May 2, 2013 by telescoper

This song was playing on the radio in the Bridge Cafe just now when I went to get a cup of coffee, thus providing me with another time warp experience. The Communards’ version of Don’t Leave Me This Way was a big hit way back in 1986 and I remember dancing to it many times in various Brighton clubs and discos; I was here at the University of Sussex then as a research student. Can that really have been 27 years ago? Sigh…

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Should the passive voice be avoided?

Posted in Education with tags , , , , , on May 1, 2013 by telescoper

It’s another very busy day (as well as another lovely one) so I thought instead of sitting indoors this lunchtime writing a typically verbose blog item I’d just pick something out of my back catalogue and give it another airing because it deals with something that’s come up a couple of times recently.

This is the time of year when final-year students are drafting their project reports. Yesterday I was back in Cardiff giving feedback on two such articles.  I usually quite enjoy reading these things, in fact. They’re not too long and I’m usually pretty impressed with how the students have set about the (sometimes quite tricky) things I’ve asked them to do for their project work. I think the project report is quite a challenge for UK physics students because they generally haven’t had much practice in putting together a lengthy piece of writing before or during their university course, so haven’t developed a style that they feel comfortable with and are often unfamiliar with various conventions (such as reference style, punctuation of equations, etc). Some of these are explained in quite a lot of detail in the instructions the students are given, of course, but we all know that only girls read instructions….

The thing that strikes me most forcibly about the strange way students write project reports is that they are nearly always phrased entirely in the passive voice, e.g.

The experiment was calibrated using a phlogiston normalisation widget….

I accept that people disagree about whether the passive voice is good style or not. Some journals actively encourage the passive voice while others go the opposite way entirely . I’m not completely opposed to it, in fact, but I think it’s only useful either when the recipient of the action described in the sentence is more important than the agent, or when the agent is unknown or irrelevant. There’s nothing wrong with “My car has been stolen” (passive voice) since you would not be expected to know who stole it. On the other hand “My Hamster has been eaten by Freddy Starr” would not make a very good headline.

The point is that the construction of a statement in the passive voice in English is essentially periphrastic, in that it almost inevitably involves some form of circumlocution – either using more words than necessary to express the meaning or being deliberately evasive by introducing ambiguity. Both of these failings should be avoided in scientific writing.

Apparently, laboratory instructors generally tell students to write their reports in the passive voice as a matter of course. I think this is just wrong. In a laboratory report the student should describe what he or she did. Saying what “was done” often leaves the statement open to the interpretation that somebody else did it. The whole point of a laboratory report is surely for the students to describe their own actions. “We calibrated the experiment..”  or “I calibrated the experiment…” are definitely to be preferred to the form I gave above.

That brings me to the choice of pronoun in the active voice. One danger is that it can appear very bombastic, but that’s not necessarily the case. I don’t find anything particularly wrong in saying, e.g.

We improve upon the technique of Jones et al. (1848) by introducing a variable doofer in the MacGuffin control, thereby removing gremlins from the thingummy process.

But the main issue is whether to use the singular or plural form. It can be irritating to keep encountering “I did this..” and “I did that..” all the way through a journal paper, and I certainly  would feel uncomfortable writing a piece like that in the first person singular. I think it feels less egotistical to use “we”, even if there is only one author (which is increasingly rare in any case). If it’s good enough for the Queen it’s good enough for me! However, I just looked “we” up in Chambers dictionary and found

..used when speaking patronizingly, esp to children, to mean `you’.

which wasn’t at all what I had in mind!

However in the case of a student project that I’m assessing I actually want to know what the particular student  writing the report did, not what was done by person or persons unspecified or by a group of uncertain composition. So I encourage my students to put, e.g.,

I wrote a computer program in 6502 Assembly Language to solve the Humdinger equation using the Dingbat-Schnitzelgruber algorithm.

I also (sometimes) like “we” when there’s, e.g., a complicated mathematical derivation.  Going  line by line through a lengthy piece or difficult technical argument seems friendlier if you imagine that the reader is trying to do the calculation along with you as you write it:

if we differentiate the right hand side of equation (8), use the expression for x obtained in equation (97), expand y in a power-series and take away the number we first thought of we find…

The “we” isn’t necessarily an  author with delusions of grandeur (or schizophrenia), but instead denotes a joint operation between author and reader.

Anyway, to resume the thread, it seems to me that sometimes it is appropriate to use the passive voice because it is the correct grammatical construction in the circumstances. Sometimes also the text just seems to work better that way too. But having to read an entire document written in the passive voice drives me to distraction. It’s clumsy and dull.

In scientific papers, things are a little bit different but I still think using the active voice makes them easier to read and less likely to be ambiguous. In the introduction to a journal paper it’s quite acceptable to discuss the background to your work in the passive voice, e.g. “it is now generally accepted that…” but when describing what you and your co-authors have done it’s much better to use the active voice. “We observed ABC1234 using the Unfeasibly Large Telescope..” is, to my mind, much better than “Observations of ABC1234 were made using..”.

Reading back over this post I notice that I have jumped fairly freely between active and passive voice, thus demonstrating that I don’t have a dogmatic objection to its use. What I’m arguing is that it shouldn’t be the default, that’s all.

My guess is that a majority of experimental scientists won’t agree with this opinion, but a majority of astronomers and theoreticians will.

This guess will now be tested by reactivating an old poll..

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Lines on the Death of Herschel

Posted in Poetry, The Universe and Stuff with tags on April 30, 2013 by telescoper

So farewell, then,
Herschel
Space
Observatory.

You were named after
William Herschel,
Who lived
During the reign of
George III.
The mad King
Who went blind,
Then died.

You went blind
Then died.
But there the
Similarity
Ends.

You ran out
Of Helium;
He had no
Need of He.

And he was neither
In Space
Nor an
Observatory,
So forget
It.

by Peter Coles (aged 49 11/12).

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Never mind the table, look at the sample size!

Posted in Bad Statistics with tags , , , on April 29, 2013 by telescoper

This morning I was just thinking that it’s been a while since I’ve filed anything in the category marked bad statistics when I glanced at today’s copy of the Times Higher and found something that’s given me an excuse to rectify my lapse. Last week saw the publication of said organ’s new Student Experience Survey which ranks  British Universities in order of the responses given by students to questions about various aspects of the teaching, social life and so  on. I had a go at this table a few years ago, but they still keep trotting it out. Here are the main results, sorted in decreasing order:

University Score Resp.
1 University of East Anglia 84.8 119
2 University of Oxford 84.2 259
3 University of Sheffield 83.9 192
3 University of Cambridge 83.9 245
5 Loughborough University 82.8 102
6 University of Bath 82.7 159
7 University of Leeds 82.5 219
8 University of Dundee 82.4 103
9 York St John University 81.2 88
10 Lancaster University 81.1 100
11 University of Southampton 80.9 191
11 University of Birmingham 80.9 198
11 University of Nottingham 80.9 270
14 Cardiff University 80.8 113
14 Newcastle University 80.8 125
16 Durham University 80.3 188
17 University of Warwick 80.2 205
18 University of St Andrews 79.8 109
18 University of Glasgow 79.8 131
20 Queen’s University Belfast 79.2 101
21 University of Hull 79.1 106
22 University of Winchester 79 106
23 Northumbria University 78.9 100
23 University of Lincoln 78.9 103
23 University of Strathclyde 78.9 107
26 University of Surrey 78.8 102
26 University of Leicester 78.8 105
26 University of Exeter 78.8 130
29 University of Chester 78.7 102
30 Heriot-Watt University 78.6 101
31 Keele University 78.5 102
32 University of Kent 78.4 110
33 University of Reading 78.1 101
33 Bangor University 78.1 101
35 University of Huddersfield 78 104
36 University of Central Lancashire 77.9 121
37 Queen Mary, University of London 77.8 103
37 University of York 77.8 106
39 University of Edinburgh 77.7 170
40 University of Manchester 77.4 252
41 Imperial College London 77.3 148
42 Swansea University 77.1 103
43 Sheffield Hallam University 77 102
43 Teesside University 77 103
45 Brunel University 76.6 110
46 University of Portsmouth 76.4 107
47 University of Gloucestershire 76.3 53
47 Robert Gordon University 76.3 103
47 Aberystwyth University 76.3 104
50 University of Essex 76 103
50 University of Glamorgan 76 108
50 Plymouth University 76 112
53 University of Sunderland 75.9 100
54 Canterbury Christ Church University 75.8 102
55 De Montfort University 75.7 103
56 University of Bradford 75.5 52
56 University of Sussex 75.5 102
58 Nottingham Trent University 75.4 103
59 University of Roehampton 75.1 102
60 University of Ulster 75 101
60 Staffordshire University 75 102
62 Royal Veterinary College 74.8 50
62 Liverpool John Moores University 74.8 102
64 University of Bristol 74.7 137
65 University of Worcester 74.4 101
66 University of Derby 74.2 101
67 University College London 74.1 102
68 University of Aberdeen 73.9 105
69 University of the West of England 73.8 101
69 Coventry University 73.8 102
71 University of Hertfordshire 73.7 105
72 London School of Economics 73.5 51
73 Royal Holloway, University of London 73.4 104
74 University of Stirling 73.3 54
75 King’s College London 73.2 105
76 Bournemouth University 73.1 103
77 Southampton Solent University 72.7 102
78 Goldsmiths, University of London 72.5 52
78 Leeds Metropolitan University 72.5 106
80 Manchester Metropolitan University 72.2 104
81 University of Liverpool 72 104
82 Birmingham City University 71.8 101
83 Anglia Ruskin University 71.7 102
84 Glasgow Caledonian University 71.1 100
84 Kingston University 71.1 102
86 Aston University 71 52
86 University of Brighton 71 106
88 University of Wolverhampton 70.9 103
89 Oxford Brookes University 70.5 106
90 University of Salford 70.2 102
91 University of Cumbria 69.2 51
92 Napier University 68.8 101
93 University of Greenwich 68.5 102
94 University of Westminster 68.1 101
95 University of Bedfordshire 67.9 100
96 University of the Arts London 66 54
97 City University London 65.4 102
97 London Metropolitan University 65.4 103
97 The University of the West of Scotland 65.4 103
100 Middlesex University 65.1 104
101 University of East London 61.7 51
102 London South Bank University 61.2 50
Average scores 75.5 11459
YouthSight is the source of the data that have been used to compile the table of results for the Times Higher Education Student Experience Survey, and it retains the ownership of those data. Each higher education institution’s score has been indexed to give a percentage of the maximum score attainable. For each of the 21 attributes, students were given a seven-point scale and asked how strongly they agreed or disagreed with a number of statements based on their university experience.

My current employer, the University of Sussex, comes out right on the average (75.5)  and is consequently in the middle in this league table. However, let’s look at this in a bit more detail.  The number of students whose responses produced the score of 75.5 was just 102. That’s by no means the smallest sample in the survey, either. The University of Sussex has over 13,000 students. The score in this table is therefore obtained from less than 1% of the relevant student population. How representative can the results be, given that the sample is so incredibly small?

What is conspicuous by its absence from this table is any measure of the “margin-of-error” of the estimated score. What I mean by this is how much the sample score would change for Sussex if a different set of 102 students were involved. Unless every Sussex student scores exactly 75.5 then the score will vary from sample to sample. The smaller the sample, the larger the resulting uncertainty.

Given a survey of this type it should be quite straightforward to calculate the spread of scores from student to student within a sample from a given University in terms of the standard deviation, σ, as well as the mean score. Unfortunately, this survey does not include this information. However, lets suppose for the sake of argument that the standard deviation for Cardiff is quite small, say 10% of the mean value, i.e. 7.55. I imagine that it’s much larger than that, in fact, but this is just meant to be by way of an illustration.

If you have a sample size of  N then the standard error of the mean is going to be roughly (σ⁄√N) which, for Sussex, is about 0.75. Assuming everything has a normal distribution, this would mean that the “true” score for the full population of Sussex students has a 95% chance of being within two standard errors of the mean, i.e. between 74 and 77. This means Sussex could really be as high as 43rd place or as low as 67th, and that’s making very conservative assumptions about how much one student differs from another within each institution.

That example is just for illustration, and the figures may well be wrong, but my main gripe is that I don’t understand how these guys can get away with publishing results like this without listing the margin of error at all. Perhaps its because that would make it obvious how unreliable the rankings are? Whatever the reason we’d never get away with publishing results without errors in a serious scientific journal.

This sampling uncertainty almost certainly accounts for the big changes from year to year in these tables. For instance, the University of Lincoln is 23rd in this year’s table, but last year was way down in 66th place. Has something dramatic happened there to account for this meteoric rise? I doubt it. It’s more likely to be just a sampling fluctuation.

In fact I seriously doubt whether any of the scores in this table is significantly different from the mean score; the range from top to bottom is only 61 to 85 showing a considerable uniformity across all 102 institutions listed. What a statistically literate person should take from this table is that (a) it’s a complete waste of time and (b) wherever you go to University you’ll probably have a good experience!

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