Guernsey McPearson


Epitaph for a Bayesian
Sequential analysis
Welsh test
Poetic fancy

Epitaph for a Bayesian

Here lies one who followed Bayes
Faithfully for all his days
Monday's prior plus Tuesday's data
Wednesday's likelihood and later
(Thursday, Friday, hesitation
waiting for the simulation
What a blessing is the PC
With Gibbs sampling it's so easy)
Sunday rested, felt superior
Safe with Saturday's posterior
Monday saw initiation
Of a further iteration
Choosing as his prior, one
That he last was sitting on

So he lived from day to day
Treading the coherent way
Each and every step he took
Written in the great Dutch book
Until one day he met his fate
Lurking by the garden gate
It had teeth and it had claws
It was crouching on all fours
Weighed eight hundred pounds at least
A most uninferential beast
As his prior told him that
It should be the neighbour's cat
With the evidence combined
Led him to the frame of mind
When updated, to assume a
Lion was a baby puma

Alas, alack for our poor man
The lion had another plan
His prior hunger proved to be
A match for Bayes' posterity
And one who could not trust his eyes
Experienced at his end surprise


Every Bayesian take this warning
Lest you be the cause of mourning
Lest the same fate you befall
Remember Cromwell's principle
And always leave a prior lump
Protector for Barebones and Rump!

Sequential Analysis

"The ane thing aye leads tae the ither,"
Was the guid rede that gave her mither
"Tae gang sae far and gang nae further
Is easy 'nough tae say
But first the lad will hae you kissed
Then lay his hand upon yer breast
And then by jings, he'll hae the rest
And willnae stop fer nay."

Noo Jenny was a comely lass
A figure like an 'oor glass
A face than nae young lad cad pass
But had tae turn his head
A bonnier girl ther n'ere was seen
A ve-ri-ta-bul beauty queen
A heartbreaker at seventeen
Who turned a' faces red.

But of the rogues a lass should curse
For pressing on tae be the first
A stat-ti-sti-shun is the worst
Seducer you cad find
An' of the stat-ti-sti-shun clan
There is a sept that takes the van
Aye in a stramash to fesh on
Once started on the game.

Despite he is no lazy one
When amrus deed is tae be done
I speak not of the Baye-si-un
Although no slouch in love
But rather of the fre-quen-tist
A thrice died divil tae be hissed
Especially when he is p****
An. push has come tae shove

Wi sic a one who nivver missed
The foolish lassy kept her tryst
Believing that when she'd been kissed
She then would call a stop
But when she said, "now you must see
That you have most sig-ni-fi-cant-ly
Traversed ma lower boundary
It's time tae close the shop."

The cairl replied, "why not at all,
For I'll be damned if I will call
It off wi'oot a pro-to-col
To say I must desist
I wonder what ye learned at school
To come and play the little fool
An' think wi'oot a stopping rule
You cad escape ma list."

Noo, all ye lassies mind the tale
An' lairn twa rules that nivver fail
If ye wad stay behind the pale
An' keep from being undone
First, always write a pro-to-col
And' second fix the stopping rule
An' see that they are known tae all
Afore the trial's begun.

Welsh Test

The Welsh are a talented race, skilled in all the arts except music. This was brought home to me very forcibly one weary night many years ago when youth hostelling in the Lake District. Sharing my dormitory was one Welsh male voice choir. Twenty gentleman singing classics of the Welsh repertoire until one o'clock in the morning is not conducive to that sleep desired by those who intend to be off at the crack of dawn (hostel duty permitting) to attack the surrounding peaks. At long last GMcP was asked, 'and can you sing anything?'. I immediately launched into the woad song, which goes to the tune of Men of Harlech. Such was the affront to the national amour propre that they were all stunned into a disgusted silence and I was able to enjoy the rest of a good night's sleep.

Imagine my surprise on discovering some years later that the McPearson family has a Welsh connection. On rummaging through some documents in the family possession I turned up a curious piece by one Geraint ap Pearson which is evidently a song to the tune of Men of Harlech. It has no literary merit but is at least on a subject of relevance and I reproduce it here in case it is of any interest to SPIN readers.

The Medical Advisor's Lament

What's the use of statisticians
When you need to make decisions?
All they do is drive physicians
Slowly round the bend
What's the use of logic choppers
Lies, damned lies and great big whoppers
Thought police, computer coppers
When you're on a trend
Sod this reign of terror
Stuff their type one error
Student's t
The dreaded P
Kaplan-Meier curves and standard error
Intent to treat a
Rotten cheater
They're' obsessed with bloody beta
Life without would be much sweeter
Let them all go hang

All this sample stuff is phoney
All their spending rules baloney
And the dreaded Bonferonni
Brings us to our knees
Just when you've a fine impression
From your last computer session
They will claim it's all regression
Rob you of your Ps
Did you pre-determine?
If not you're just vermin
It's a shock
To find post hoc
Is not accepted as a way of learning
Group sequential
In your trials experimental
Is the stuff to send you mental
Pass the Prozac please.

Frequentist approach you courted
Just when you had got it sorted
They the paradigm aborted
Made you change your ways
Every lesson that you heeded
It turns out is not now needed
It has all been superseded
You must turn to Bayes
It's not what you desire
Now the stakes are higher
May well be good
But now they pester you about your prior
Makes you wearier
Brings hysteria
If you want to feel much cheerier
Shove it up their damn posterior
Let them feel surprise!

Poetic Fancy

Dundee is famous for three things they say: jute, jam and journals. Jute was once the basis of a flourishing textile industry and it was in Dundee that the resourceful wife of greengrocer James Keiller saved the day by boiling up a load of bitter Seville oranges with some sugar and thus invented marmalade. (And if this isn't true at least the story has appeal.) The journals are those of DC Thomson which publishes a range of titles including the Scots Magazine and the children's comic The Beano. But...Dundee has a fourth claim to fame for it was here that the poet William McGonagall composed and recited his famous verse. What is little known is that he was also a prophet, for an obscure unsigned MS in the possession of the McPearson family can be by none other than the great William McG and, for a nineteenth century poem, seems to have strange precognisance of events to take place in the late twentieth century. Here it is....

Twas in the year nineteen hundred and ninety-eight
That I said please hurry and don't be late
For in the month of August there will be
A meeting of the ISCB
So hasten you all to bonny Dundee
And we shall meet for biometrics
And have a dinner and go on fine trips
And hear many an interesting talk
(And even at boring ones we'll not balk)
For are we not medical statisticians
And true and trusty: unlike politicians?
So in the centre you may gather
Or wander through the town if you'd rather
And learn about parallel trials and ANCOVA
Or go to Fife on a cross-over
By road or by rail on a bridge of the Tay
For either is fine if you'd cross for a day
For the last time one broke was in 1879
Which will be remembered for a very long time.
We'll meet at our AGM for a blether
And gang for lang walks o'er the bonny heather.
And then, when the meeting is done
And we have agreed that we all had great fun.
We shall all take our leave of bonny Dundee
And pledge next to meet in far Germany.

Next issue. Parley voo Dundee? Here is an apersoo. Scene 1 at the bakers: How to order 'two pies: a plain one and an onion one as well,' in true Dundonian. Scene 2 at the greengrocers: 'er ye gettin yers dearie?' and 'gie us a naple,' translated. Scene 3 at the conference dinner: 'bashed neaps and champitt tatties', 'I'll hae a dram,' ,'where do you stay?', 'fur coat and nae drawers' etc. Scene 4 at the AGM: 'he's an affie man', 'show us the short leet', 'it's outwith my jurisdiction', 'what are the intimations?' 'can I have that homologated?' and other curious phrases explained. Scene 5. In the restaurant. 'Will you have apple peh or a meringue?' 'Nae yer not wrang; I'll hae the apple peh.'