Experts warn Letby inquiry of misreading stats to explain 'suspicious' deaths • Hacker News Board

Re: Experts warn Letby inquiry of misreading stats to explain 'suspicious' deaths

#91

Post by oh_sigh » Wed, Oct 11, 2023, 3:11 PM UTC

gus_massa wrote: post #90

YeGoblynQueenne wrote: post #85

Earlier quoted context omitted.

I made another post yesterday on the argument that "that the suspicious deaths all lined up perfectly with Lucy Letby's shifts": https://news.ycombinator.com/item?id=37814339 Those arguments, as presented to the jury, relied entirely on a spreadsheet of the nurses' duty roster. There's an image here (on the Daily Mail website): https://i.dailymail.co.uk/1s/2023/08/18/22/74487747-12286051... Looking at this spreadshee…

> It is very difficult to believe that there were no shifts were incidents occurred and Lucy Letby was not on shift, or times Lucy Letby was on shift but no incident occurred. I agree. It's very strange that there was not at least one case when she was not there. Death are very clear, but it's easy to use different criteria to classify an weird case as suspicious. I'd expect more cluster of nurses. There are a few th…

Infant mortality is something like 3.3 per 1000 in the UK. 25% of that happens in the first week, and women are usually discharged with their baby after 2 or 3 days. And that mortality rate includes things like known defects that are incompatible with life that would not be considered suspicious when the baby dies.

So, there should be far fewer than one death per thousand of the newborns in the hospital. Since her activities took course over a year, it's quite possible that no unexplained deaths happened apart from the ones that she was involved with.

It's also possible there might be one death not caused by her that just happened to occur on her shift.

Re: Experts warn Letby inquiry of misreading stats to explain 'suspicious' deaths

#92

Post by YeGoblynQueenne » Wed, Oct 11, 2023, 6:14 PM UTC

oh_sigh wrote: post #91

gus_massa wrote: post #90

Earlier quoted context omitted.

> It is very difficult to believe that there were no shifts were incidents occurred and Lucy Letby was not on shift, or times Lucy Letby was on shift but no incident occurred. I agree. It's very strange that there was not at least one case when she was not there. Death are very clear, but it's easy to use different criteria to classify an weird case as suspicious. I'd expect more cluster of nurses. There are a few th…

Infant mortality is something like 3.3 per 1000 in the UK. 25% of that happens in the first week, and women are usually discharged with their baby after 2 or 3 days. And that mortality rate includes things like known defects that are incompatible with life that would not be considered suspicious when the baby dies. So, there should be far fewer than one death per thousand of the newborns in the hospital. Since her ac…

Note that the babies involved in the incidents were premature, and mortality for premature babies is going to be lower than that for full term babies.

Further, as I understand it, those were babies that were being cared for in the Neonatal Intensive Care Unit and may have been vulnerable and less likely to survive to begin with.

For example, I remember the press noting that a baby who died was no bigger than a hand. The press reported this to tug at readers' heartstrings, but it also has the effect of reminding that a baby born so early is in a precarious situation and may well not make it.

In any case, the spreadsheet above doesn't give any of that information, either, so there is not enough information to know whether the deaths were suspicious in the first place. Looking at the spreadsheet, all we can say is that the only reason those incidents are associated with Lucy Letby is because Lucy Letby was on shift. Which is a tautology and not useful to make any decisions.

Re: Experts warn Letby inquiry of misreading stats to explain 'suspicious' deaths

#93

Post by gus_massa » Wed, Oct 11, 2023, 8:36 PM UTC

oh_sigh wrote: post #91

gus_massa wrote: post #90

Earlier quoted context omitted.

> It is very difficult to believe that there were no shifts were incidents occurred and Lucy Letby was not on shift, or times Lucy Letby was on shift but no incident occurred. I agree. It's very strange that there was not at least one case when she was not there. Death are very clear, but it's easy to use different criteria to classify an weird case as suspicious. I'd expect more cluster of nurses. There are a few th…

Infant mortality is something like 3.3 per 1000 in the UK. 25% of that happens in the first week, and women are usually discharged with their baby after 2 or 3 days. And that mortality rate includes things like known defects that are incompatible with life that would not be considered suspicious when the baby dies. So, there should be far fewer than one death per thousand of the newborns in the hospital. Since her ac…

From https://en.wikipedia.org/wiki/Lucy_Letby

> The numbers of unexplained collapses were particularly abnormal: there had previously been only two or three deaths a year in the neonatal unit.

She was convicted for cases between June 2015 and June 2016, so I'd expect to see like 2 or 3 cases of natural deaths. Assuming she works there for 40 hours of the 168 hours of the week, it's like 1 coincidence and 1 or 2 when she was not there. Been there when 7 babies died is a LOT of bad luck.

Assuming a Poisson distribution with lamba=2.5/4, P(7)=7E-13 ...