UKH

https://twitter.com/BorisJohnson/status/1259572964447653892

Hope that's clears up any possible confusion. 

I assume the + should be a X.

It would make sense then.

Anyone else get the impression that no one in government seems to have a basic grasp of maths?

Thought the same thing.

Formula fails dimensional analysis ergo it’s nonsense.

R × (number of infections) is a pretty good alert level, normalised to hospital capacity and average hospitalisation time and mapped to 1-5 you’d get something quite sensible.

L= [f(R,N)]

I still have no idea what it means. Using their formula, today's Covid Alert Level is 219,183.7. Even if we change the + to x, which makes more sense, it's still a very high number (153,428), which will be increasing every day. So, as the alert level goes up, the risk goes down and the lockdown can be eased. Is that it? I've just no idea how we're meant to use these figures. I'm so alert now that I've looked under my settee, but still haven't spotted any coronaviruses. Perhaps I should be using a magnifying glass ??

Surely this 'Alert Level' thing is a meaningless farce?

BTW, how is the R figure calculated, if we're only testing a fraction of the population?

Dear Robert, Could you please explain your formula for non-mathematical mortals like myself.

Well you wouldn't Gordon.

If I told you Reynolds number for a liquid flowing down a pipe was 110 you wouldn't have a clue either but I could get a lot from it as could many engineers.

Essentially it taking two important metrics and combining them. How infectious the disease current is and how many people have it. If you think about it, multiplying them together tells you how many more or less people will have the disease tomorrow.

You do need to know a bit about the modelling to figure out what a particular value implies but presumably the epidemiologists know that. 

What's good about this measure is that it makes decision making objective. When a number falls below a certain value restrictions can be relaxed and vice versa. No doubt as we progress those points at which we change will be adjusted but at least we're not guessing.

I get the principle, but if that big figure starts going down, as the R number drops, doesn't that merely put us back to where we were 2 or 3 weeks ago, when it was deemed essential for us to be locked down?

I'm guessing they have much more complex modelling they are using to decide whether or not to relax the lockdown but that's not something you can put into a tweet and so they've tweeted this nonsense instead.

No, because R will have been higher before lockdown.

clearly a bolx equation, but taking n and R into account is clearly sensible.

It just means that the alert level is going to depend on both the infection rate and the number of infections and will be rounded off to a whole number. This is what Boris tried to tell us in a naff mathematically illiterate way! Not that my way would be any more helpf to the general public.

L (the alert level) is* a function (f) of 2 variables, R (infection rate) and N (no. of cases).

* or, more accurately would be if there was a grown up in charge.

Phew, another committee to advise the government! That virus must be quaking in its boots.

I think it would also be fair to assume that the partial derivatives of f with respect to both R and N will be positive for all F and N (unless there is a point where we say "f*** it, we're all going to die anyway, so we might as well go climbing beforehand")

If dR is negative (infection rate falling) but dN is positive (number of cases still rising, but slower?) would dF still be positive?

Current alert level: Twelvety thousand and dozen.

Are you local?

Where are they getting the number of infections from?

<Sarky Mode> Is it our extensive testing system we have in place? </Sarky Mode>

FTFY

Twelety thousand and dozen point seven.  (You forgot to add 'R'.)
Seems quite high on a scale of 1-5 doesn't it?

Is it Wednesday this formula comes into force?  Should be really: it's 'National Numeracy Day'. 
Perhaps Dianne Abbot could ask Priti Patel to explain how the numbers work, clear up the confusion once and for all.

Why on earth is anyone getting hung up on this? It's a simple way of communicating to the public that the alert level is dependent upon a combination of two factors. The slide is not a mathematical formula that anybody is going to use, it's a communication tool.

The only explanation of this 'formula' I have heard that makes any sense is that it is not intended to be read as a formula.

Therefore it is not that the Covid Alert level is equal to the rate of infection added to the number of infections.

Rather, it is meant to show that the Covid Alert level will somehow be based on/derived from the two elements on the right of the equals sign but that these two elements will not be added together(even though that is what the equation indicates).

The best interpretations I can arrive at is someone in No.10 does not understand what " =" and "+" means, or they are trying to blind the populace with science.

Dave

Because we like taking the piss?

Doesn't even define 'number of infections'  could be:

a. number of new infections per day

or b. number of active infections

Details schmeetails. Terrifying really.

jk

Where do you think they advertise for their scapegoats?

jk

Because they could have explained how they intended to measure the levels of "alertness".

Truth, clarity and openness, is that too much to ask for?

Of course it is not.

That should be obvious to anybody who is mathematically literate and the intended message should be obvious to anyone who is mathematically literate or not.

I don't really have a problem with it. I think the only reason to have a problem with it is if you are going out of your way to see trivial faults with the government which aren't actually there (and I say this as a mathematically literate person who has no problem finding real faults with the government).

Obviously.

Neither. They are just getting a message across in a concise but not mathematically literal way.

It is really no worse than using the word "energy" in a way that not consistent with it's precise scientific meaning.

It would definitely make more sense than a + but would still be an ineffective measure.

A r of 0.5 and 1,000,000 cases would get the same alert level as r =2 and 250,000 cases. In reality 10 days later the hospitals would look very different for the same alert level.

If only they had a scientist handy that they could ask for advice...

With all the fanfare that this was announced with, would it be valid to ask if, where and what frequency (daily, weekly) this figure is being published by the Govt?

Perhaps if the government were trying to get a message across in a concise but not mathematically literal way it would have been simpler to say -

the Covid Alert level will be based on the rate of infection and the number of infections -

rather than using a formula with common mathematical symbols.

Dave