Wednesday 22 December 2021

False positives

There are two kinds of error in medical diagnostic tests: the test indicates negative when there is disease present, or positive when there isn't.   Given that a person either has the disease or doesn't, and tests positive or negative, these four are the only possible outcomes:

  • Patient has the disease and tests positive - GOOD
  • Patient has the disease and tests negative - BAD
  • Patient doesn't have the disease and tests negative - GOOD
  • Patient doesn't have the disease and tests positive - BAD
The error rate for a diagnostic test is therefore fully specified by two statistics, labelled as % false positives and % false negatives.   Fine so far.

The problem is that the % false positives is not the percentage of positive test results that are false, although it sounds like it should be.  It is the (average) percentage of people who don't have the disease who none the less test positive.  The two things are very different.

To illustrate, let's consider an imaginary diagnostic test - a good one.   Let's suppose our test has a false positive rate of 1% and a false negative rate of 0%.   This would be an extraordinarily good test - I don't know if any tests available today meet these criteria.

Let's now suppose that we roll out this test on a population where the true rate of infection is, say 500 per 100,000.  (That is, 5 per 1000, or 1 for every 200 people) This kind of infection rate has our political leaders losing control of their anal sphincters, so it's a "bad" scenario. 

Let's test 200 of these people, chosen at random.  On average there will be one person infected, and our excellent test always indicates positive for that person.  But we also get around 2 false positives (1% of 199).  So if you are a member of this population, and you test positive, the chance that you actually have the disease is about 1 in 3, that is 33%, and the chances that you don't are about 67%.

If the false positive rate of our test was 10% (a more realistic figure), a positive test result would mean you had only a 5% chance of having the disease.   If the true infection rate were lower, the chances of having the disease if you test positive would be (even) lower. 

Wednesday 15 December 2021

Accordeon at Le Mans

Richard Galliano is a renowned accordeon player, and he gave a concert recently at the Palais des Congrès et de la Culture in Le Mans.   He was playing alongside the strings from the Orchestre Nationale de Pays de la Loire, conducted by Mme Alexandra Cravero, in what was billed as a tribute to Piazzolla, an Argentinian composer who is remembered for introducing the tango into the classical music repertoire.

We had decided to make a day of it, and went in time for lunch at the Auberge des Sept Plats, and then did some random shopping.   We had booked a room at a Chambres d'Hôtes just down the road from the concert, to minimise walking, and to avoid a long drive home late at night.

The official check-in time for the Chambres d'Hôtes was 5 PM, and we had some time to spare, so we found the place and Anita went and asked the man there if we could check-in a bit earlier.  He said there would be no problem after 4:30, and to park outside.  So we did.  Surprise.  After we rang the bell, a woman opened the window, told us we couldn't park there, and we couldn't stay anyway because she was ill.  And besides, she runs the place, and not the gentleman Anita had spoken to earlier.  I don't think I've ever experienced a more hostile reception.   We sat in the car and phoned the Ibis just down the road, and, being assured that they had plenty of rooms, drove there and checked in.

The concert was excellent.  Richard Galliano provided the musical excellence that one expects of a master; he played an accordeon for most pieces, and a bandoneon for Piazzolla's concerto for that instrument.   

The Ibis hotel to the north of the railway station was very friendly,  and with a bit more comfort and character than one might expect of a hotel aimed primarily at the business traveller.   It also provided a superb breakfast that lasted me nearly all day.

Thursday 9 December 2021

Submarine museum

I didn't know that there is a submarine museum at Gosport, but I saw a poster for it on the way from Portsmouth dock to my sister's place.  I decided to take a look.

I think that I was the only visitor at the time, so I got a personal guided tour of the big sub on display, HMS Alliance.  I expected it to be cramped inside, but when you think that a crew of 64 men was on board, that water was scarce and they didn't wash much, I can't imagine what they smelt like when they came ashore.

There were many interesting exhibits, so here's just a few that I found especially interesting:  A B40 communications receiver.  When I was a kid, I had a friend who had one of these, and we listened in to the radio hams around the world.   The wonders of SSB transmissions, and the strange sounds of the wireless world.  Actually the sub had a B41, but it was as I remember the B40, although smaller than I thought.

How about these for a bunch of push rods and rocker arms?  I bet the make a racket when they're going.

Apparently, submariners would keep the beer in the torpedo tubes to keep it cool.  I was sadly informed of The Great Beer Tragedy when the tube was evacuated without checking for beer first.

In a different part of the museum I came across this massive piece of ironwork.  It looked solid and must weigh several tons.  It is a chain tester; it was used to test the breaking strength of chains.  Here's the thing:  it was bought second-hand in 1901 and was in use until 2020.  That's more than one hundred and nineteen years of useful life.  I think we have become too complacent about things that stop working after 10 years or even less.

Finally, there was a squirrel in the grounds, cue my latest offering in my portfolio of wildlife pics, in an attempt to be accepted as a BBC wildlife photographer.

Wednesday 8 December 2021


While in England I decided to revisit some old haunts.   I have fond memories of wasting time along the river Meon, floating model boats that I had made, or just exploring.  It's less friendly these days, but still pretty, if only viewable now from the road.

Titchfield Abbey is still magnificent, spotlit in the evening, and the Fisherman's Rest, scene of many under-age drinking bouts, (at least, in my day) is still in business.

I wonder if I was a young teenager, I'd still be able to do what I used to there.  I doubt it.   I wonder what I'd do instead.

Tuesday 7 December 2021


This year I had the opportunity, not to be missed, of visiting the RAF museum at Tangmere before it closed for the season.   I took it.   I used to fly gliders there when I was a member of the Air Training Corps, and I have fond memories fo the place, so I went to see what they were up to.  The airfield itself has been turned over to growing vegetables, but some of the buildings remain.

I found it to be a fitting tribute to the people who flew and died, and learnt some interesting facts.   I didn't know that the RAF lost nearly 1,000 aircraft and the corresponding number of pilots in the evacuation of France, nor that Douglas Bader ran the training school at Tangmere towards the end of his career.

There was a lot of information about the pilots and the history of Tangmere, with example aircraft and flight sims that you could use.   Everything that you could reasonably hope for or expect in a museum of this kind.

I also noticed an atmosphere, a feel of the place if you like.   It was staffed, as far as I could tell, by ex-pilots and ground crew who were giving their time to help keep the memories alive.  They had "been there, done that", and had nothing to prove.  They were friendly and pleasant and knew their stuff.   I'm glad I went.

Monday 6 December 2021

There and back again

The trip to England was well planned, all sorted, until the Haunted Haystack announced that the arrival of the new MORONIC variant of our favourite bug warranted some changes to protocol.  He told us that we'd have to have to self-quarantine until our "day 2" covid test, now to be a PCR test and not the lateral flow test that we had booked and paid for, gave us a negative result.  But he didn't tell us when these changes might come into effect.

The problem was not just the waste of two days stuck indoors, out of a week in England, but the Tuesday of our planned arrival was the last day that the RAF museum at Tangmere would be open this year.  A lifetime ago, I flew gliders at Tangmere and wanted to go back to see what they had done.   This year we were visitng England early enough to go there.

The announcement was made on Saturday, and the necessary information appeared on government website on Sunday morning.  Shit!  The new rules took effect from 04h00 on Tuesday when we were scheduled to arrive at Portsmouth at 06h30.   Can we get an earlier ferry?  Departures from Caen were fully booked for the Monday, how about St Malo?   Yes, space on the ferry on Monday; it's a daytime crossing, can't be helped, book it.

And now the admin.  The cat boarding kennels are shut on Sunday, can we get him in?  Apologetic phone call, yes we can.  Piano lesson to cancel.  Can my sister put us up a day early?  Yes she can.  And while this is going on, Anita sends an email to the testing company -Prenetics-  and the conversation runs like this (paraphrased):

    - Is it possible to change the order from a lateral flow to a PCR?
    - Your request has been received and is important to us
    - Disregard my request because we don't need it
    - When the new regs come into effect you will have to upgrade to a PCR - feel free to contact customer support

But since we're now going early to avoid the new rules, we don't wish to, so we leave it at that, since we don't want to change the order.

Phew, now we're on the ferry.  Sorted, right?

Wrong.  Anita calls up Prenetics, just to confirm that all is well with the order for the Day 2 lateral flow test, and discovers that the order has been cancelled.   She then ends up in an argument with the person on the "help desk" who tries to tell her that the new testing rules apply right away (they don't)  and that a PCR test is now mandatory (it isn't).  Regardless, we can't buy the cheaper tests any more and have to get the more expensive ones.  *sigh*

So the bottom line is that we heard the news, changed the ferry to one that got in 6 hours earlier, and I got to visit the Tangmere museum.  It weren't that simple, though.

Sunday 28 November 2021

Can you dig it?

I suppose that little phrase dates me....

The ground at our place is stony.   Actually, it's rocky rather than stony.  The earth is good, nutritious, somewhat clay, but full of rocks.   They vary in size from fist-sized on up, and if I want to bring a new area into cultivation, I have to get the rocks out first.

Cue friends from up the road, and one in particular, who owns the digger shown below.  He's been over the areas I need, shovelling up the rocks to free them from the soil.  I followed the digger around, taking the newly-exposed rocks off the surface, and am now going over the areas with a fork to get the ones that are still buried.  Now that the soil has been loosened, it's a lot easier than using a pick-axe, which is what I was doing before.

I am using the rocks to build a wall.  I have the feeling I might run out of space for the wall before I run out of rocks.

Monday 22 November 2021

Dead light

A recent check of the trailer lights showed that the left-hand red rear light that should come on with the headlights wasn't working.  All the other main lights seem to be OK.  No problem, I can change the bulb.

First, take the bulb out to see what kind it is, and also confirm that one of the filaments is dead.   So I undo the two nuts on the back of the mounting, to discover that they hold the bulb enclosure onto the chassis, and undoing them doesn't give access to the bulbs.  So I bolt it back on, and undo the three screws at the front.

I take out the bulb, test it, it's fine.  Hmm problem is elsewhere.  I shuffle myself under the trailer to try to trace the wiring.  After spending some time doing this, I notice that the white bulb at the front on the left is also not working, neither is the left-hand one that lights up the number plate.  Hmm problem is somewhere along the supply to that side.   Possibly the plug (trailer) or perhaps the socket (car).   So I download and copy a plug connection diagram from the web, and identify the two connections (power and earth) for the left-hand bulbs.

After spending a while checking these out, I realise that the strange results I am getting are because the diagram shows the plug from the pin side and not the wire side, so I start again.  I confirm that the plug connections see a resistance consistent with there being light bulbs correctly connected to it.   Time to check out the socket.

So I check the socket and there is a voltage on the correct pins when the headlights are on.   At this point I'm not sure what's happening, but there's a last test to do, which is to put 12 volts onto the plug pins and see what happens.  

At this point I should mention that Anita is sometimes sceptical about my purchases of things that I tell her will probably come in handy one day.  A case in point is the variable power supply that I bought for use in those situations when I need to reliably supply a voltage to check something out (or charge batteries).  This fine device is what I now use to see what happens.

What happens is that all three of the left-hand trailer lights come on as they should.  So the only thing left is that the plug is not connecting properly to the socket.  So I bend the socket pins to make a more reliable connection.

Problem solved.  And I thought it was going to be a quick bulb change.

Friday 19 November 2021

Dead kit

Been having a spot of trouble recently, with my Slim Devices Transporter.   It is a streaming audio player; it reads the files from my file server and plays them over the stereo.

A few months ago it stopped working.  It wasn't finding the files on the server.   Tech support were helpful - it was due to an "upgrade" of the software on the server, that meant that the Transporter no longer worked.   This was deemed acceptable as an "end of life" process for the device.  It was about ten years old, and physically working fine, so that kind of thing annoys me.  We fixed the problem by "downgrading" to the software that actually worked, and all was well for a while.

More recently a mains power outage and surge fried my friend's boiler's circuits just down the road, and shortly afterwards when I try to use the Transporter, it doesn't work, again.  Wierd fault: the vu meter needles move so it thinks it's playing something, but nothing's coming out of the audio outputs. Not electrical digital, not optical digital not analogue audio.   I tried everything I could think of.

It was only when I had disconnected it from my stereo in preparation for chucking it out, that I thought I'd do one last test, since what I hadn't done up to that point was disconnect it from the mains and reconnect it.  It's one of those things that doesn't have a proper mains switch, but goes into standby mode when you turn it off, ready to respond to a remote control.  So I plugged it back it, and blow me down, it worked.

But I think it's trying to tell me that I need to start thinking about alternative arrangements for my stereo.

Thursday 11 November 2021


1) Sars-Cov-2 is a nasty virus that can and does kill or maim.

2) There exist cheap, safe and effective prophylactics, acces to which I have been denied by government edict.

3) There exist cheap, safe and effective treatments, access to which I have been denied by government edict.

4) The vaccines can only be termed vaccines after the world health organisation changed its definition of vaccine so as to include them.

5) The known short-term side-effects of these vaccines make them the most dangerous vaccines ever deployed.

6) The long-term side effects of these vaccines are unknown.

7) I am being coerced into taking these vaccines by threat of exclusion from the culture into which I was born.

8) I am angry.

Monday 8 November 2021


DIY tip:  When renovating the dormer windows, and moving from one window to the next, take down the little ladder from the roof before moving the big ladder.

Friday 5 November 2021

Cherry on top

Well I suppose you could argue that it looks a bit like a cherry, but the finial is finally on the top of the tower, indicating the end of the work.   The zinc skirt posed a bit of a problem:  the roofer took the measurements, cut the zinc cone at home and came back to fit it, but the roof isn't exactly conical, so the skirt didn't sit right.  He fixed it by tracing around the edge at a fixed distance from the tile edges.  I think he took a bit off the mounting wood too.  But now it all looks shiny and new (and vertical).  Scaffolding is now down and packed away.

Monday 1 November 2021

New season

The Summer crops are all done, the Autumn harvest of butternut and other squashes is in, and the Winter crops are still in the ground.   So it's time to think ahead and prepare for next year.  And at the same time, take stock of the storm damage.

The cheap plastic greenhouse is no more; the storm finally did for it, tearing the rip-stop plastic cover into several pieces.  The frame survived; it was tied to iron rebar stakes that got bent, but held.  I might divide it into two climbing frames for roses or something, but I'm not going to try to remake a greenhouse from it.

The area of ground in the second picture is newly cultivated this year.  I put down two tarpaulins to keep the weeds down, and planted the squash into holes in them.   You can see the weed-free areas where they used to be.   For next year, I got a load of horse manure from Joël up the road, spread it out on the ground, soaked it thoroughly with water and covered it with the tarpaulins.  I'll plant squash and melons there next year. 

The bare areas where the tarps were this year, I'm pick-axeing to get the rocks and stones out.   These are being used to build the wall behind the ex-greenhouse.  I have a trailer load of compost from the recycling depot at Chammes that I will put on the area, plus some more manure from Joël, and the plan is for potatoes there next year.

Thursday 21 October 2021

Junk food labels

There was a funny item on the TF1 news the other night.   First, some background:

The French are very particular about their food, and also about it being the genuine article.   You can call pretty much any cheese cheddar in England, regardless of whether it comes from Cheddar or not, as long as it looks and tastes vaguely like cheddar.   They didn't protect their mark.   

This is not so in France.  For example, they stomped down pretty hard a few years ago, against the then-growing tendency to call any fizzy white wine "champagne" even if it didn't come from Champagne.  (Everyone except the Russians knelt before this, but (again according to TF1) the russkies call their own fizz "champagne" and they also call the French champagne fizzy wine, just to rub salt into the wound)  Even the "Methode Champegnoise" description for fizz that indicated that it was made in the same way as champagne, was outlawed and had to be replaced with "Methode traditionelle". 

The idea is that in France, people will easily be able to identify The Real Thing from imitations of lower quality.   They have various categories of protection, AOP is a common one, meaning "Appellation d'Origine Protegée, that is the food you are buying is The Real Thing, from The Actual Place and made to a Recipe that is clearly defined and is Not Allowed to Change.

Moving on, our unelected lords and masters in Brussels have decided that it's a good idea that good, nutritious food be distinguishable from inferior food by means of a "nutri-label", that classes the food from A to E, A being Very Good For You and E being rather less so.  Fine so far.

Roquefort is a cheese that I adore, it's an AOP cheese, made from raw sheeps' milk, made in a fixed way, and innoculated with penicillium, giving it a "blue" aspect.  It's flavourful, has lots of salt and is high fat, and accordingly has a nutri-score of E.   The makers of the cheese are somewhat miffed, since as they point out, they can't change the recipe and still call it Roquefort, but producers of inferior imitations can change the recipe of whatever they produce that mimicks Roquefort in taste, appearance and creaminess, and thereby get a better nutri-score.

So, The Real Thing is bad for you, but the inferior imitations are good.   I nearly wet myself laughing.   

Thinking farther ahead, what are the odds, do you reckon, that the insects they're trying to persuade us will be good to eat will be classed "A"?

Friday 15 October 2021

Scalloped decoration

 A ring of curved tiles.

Monday 11 October 2021

Tiles going on

Slow, because each tile is individually trimmed to size and shape, then nailed on with two stainless steel nails.  What you see here is nigh on a day's work.

Getting the lines right

Our roofer is putting the tiles on from today.   One of the key aspects is getting the lines of tiles correct.   To this end he has made vertical lines converging at the top, and today is using a giant wooden compass, constructed on the spot, to make the horizontal ones.

The wooden beam is pivoted at the top of the tower, and rotates around it.  The pencil is held in place by a bracket that is screwed on, and is moved up the wood in increments corresponding to the length of the tiles.

Saturday 9 October 2021

The commune

The commune of St Pierre sur Erve has a population of about 144 people, if no-one's away on holiday.   The cost of maintaining the local school falls to the residents, and money is not to be recklessly spent.   A call went out from the mayor a couple of weeks ago for volunteers to help paint the school's outdoor woodwork.   About 14 of us turned up.

Paint and brushes were supplied of course, and the reward was a free lunch afterwards.   A second coat of paint is planned for some time in the future, but meanwhile, I don't think it looks bad.

It was quite a social affair, and the widow of our old mayor came over with coffee and biscuits mid-morning, just for the participation; much appreciated by all.   It seems to me that if our society is going to focus more on local communities in order to function in future, St Pierre sur Erve has a head start.

Friday 8 October 2021

The curse

Didn't I say, just the other day, that a new and excellent coffee and bun shop had been set up in our local DIY shop?   I guess that was the kiss of death.

Tuesday 5 October 2021

Wood on the roof

The tower is now getting its second layer of wood.  Rain poured down here over the weekend; 60mm along with strong winds on Saturday night.   Fortunately the tarpaulin held, and no significant amounts of rain came into the house.  

 Other parts of France had even more rain, and flooded houses are again appearing on the news.

Monday 4 October 2021

Leroy coffee

Leroy Merlin is a well-known chain of DIY shops; our nearest one is in Laval.    They used to have some fairly naff coffee available to customers, but they have recently installed what appears to be a Nespresso franchise coffee and bun shop.   We checked it out the other day, verdict: not bad at all.   We'll use it again, I'm sure.

Tuesday 28 September 2021

New tower roof continued

Materials delivered, old slats coming off, wooden frame made good, then new slats going on.   The slats have been soaking for a couple of days in a wooden bath, constructed on the spot, to render them more flexible for nailing down onto the round roof frame.

Saturday 25 September 2021


I planted a few Sunflowers last Springtime, just to see if they would grow.  They flowered well enough and here is one picture of the result.  The thing I notice is the near-perfect arrangement of seeds, and the question I have is "why haven't the sparrows eaten them all"?

Friday 24 September 2021

New tower roof

It was time to repair the conical roof of our tower.   The tiles were falling off and looking tatty, and there was evidence of leaks.   We engaged a local roofer, he lives in the village and does good work.   Since we're in an SPR "Site de Patrimoine Remarquable" the local state architects had their say, but OK'd the project in the end.

Days one and two, the scaffolding went up, the old chimney came down, and the tiles came off.  The finial was interesting; it was full of holes (.22 cailbre) that you couldn't see from the ground.  Apparently the local hunters used them as target practice. 

The pile of leaves you can see in the first picture is Wisteria that we had to cut away to make room for the scaffolding and to get it off the roof.   Something else of note is that the price estimate had to be increased due to the rocketing price of building materials.

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