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Boeing admits flaw in 737 Max flight simulator

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Boeing admits flaw in 737 Max flight simulator

Old 23rd May 2019, 10:49
  #81 (permalink)  
 
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Originally Posted by bill fly View Post
Hi Jodel,
I think we should distinguish between average folk and average professional pilots in this argument.
Pilots only get (and stay) where they are after stringent selection, training and repeated checking. They are a small part of the community.
That doesn’t mean they have to be especially clever or elite - but just ideal people for their job. Other people are ideally suited to other professions, at which many pilots may fail.
A professional pilot should be well up on your scale - if that scale applies to flying skills/aptitude as applied to the general community. The bad ones get found out with very few exceptions.
A doctor or an architect doesn’t go through this process - has to prove him(her)self to stay in business in other ways...
So an aircraft designer has the right to expect a certain level of skill. I seem to remember in my manual, that Boeing were pretty clear on the skill tests their pilots were expected to pass. That needs to be borne in mind when using terms like “average”.
On the other hand, a professional pilot has the right to expect a level of skill from the manufacturer. This includes honest self criticism such as is required of a professional pilot.
B
Jodel in his graph made clear that represent from "barely pass certification" to "top gun", which if my understanding correctly represent the total number of professional pilots.
He is already distinguishing between average folk (me) and average professional pilots.
There will be always an average, no matter how high you set the bar, some will be above the average and other below the average.
In fact, in my opinion, he has a very good point. Aircraft certification requires that the design is made for average certified professional pilot, which implies that a number (no matter how stringent is the certification process) of professional pilots will not fall in that category, therefore he is suggesting to have system designed (for aircraft certification purpose) for every certified professional pilot (not the average).
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Old 23rd May 2019, 10:55
  #82 (permalink)  
 
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Originally Posted by bill fly View Post
Hi Jodel,
I think we should distinguish between average folk and average professional pilots in this argument.


We are.

Originally Posted by bill fly View Post
Pilots only get (and stay) where they are after stringent selection, training and repeated checking. They are a small part of the community.
According to wikipedia, there are 290,000 airline pilots worldwide.

Originally Posted by bill fly View Post
That doesn’t mean they have to be especially clever or elite - but just ideal people for their job. Other people are ideally suited to other professions, at which many pilots may fail.
Yes, that's why they are pilots.

Originally Posted by bill fly View Post
A professional pilot should be well up on your scale - if that scale applies to flying skills/aptitude as applied to the general community. The bad ones get found out with very few exceptions.
This paragraphs seems to indicate either:

a) lack of understanding of basic statistics / probability

First of all, the picture above is not a scale, it's a distribution where 100 represents the average pilot. There will always, always be pilots who are below average and pilots who are above average. The question is, how below average is the worse commercial pilot currently flying (and how good is the best one on the opposite side).

The only thing that could be up to debate is weather the standard deviation is small (blue graph) and all pilots are almost equally good in skills, or is it (in the extreme) like orange graph and some pilots are way worse than the average pilot.

I don't have the data to support either of the cases. I hope we are closer to the blue graph, but... are we?

Interestingly, Boeing - by blaming the pilots for recent crashes - is saying that there is a wide gap between average and sub-average pilots AND that their airplanes are only meant for average skilled pilots, which in essence means, Boeing is saying the current certification is to permissive (you can't accept the current pilot certification as acceptable AND blame the pilots, it's a contradiction).

b) all pilots are exactly equal

You need to believe that all pilots are exactly the same if you are saying there is no distribution. Oh, I hear you, you are thinking "but that's not what I said, what I said is that the bad ones are filtered out".

Then we are back to a). Because, if you have pilots who have skills 89,93,100,101,110, the average is 98.6. You filter out the bad ones and end up with 93,100,101,110. Now your average is 101, but that is not above average, that's just the new average. Now the pilot with skill of 100 is below average. By pruning the bad ones you are improving the average, but the distribution is still there

There is another phenomena, if the airplane manufacturers are truly targeting "average" pilot, and that average goes up, the number of pilots who can handle the plane properly will decrease, simply because there are just so many pilots who are at or above average, which is a problem.

According to wiki quoted above, Boeing expects 790,000 new pilots in 20 years from 2018. What will their skills be compared to the current population, where we still have pilots who are not "children of magenta"? Where will the average move in the next 20 years with so many fresh pilots AND old pilots retireing? My bet is, it's going to go down cosiderably, while the airplane manufacturers are building planes for just the best of them. If that is the case, perhaps MCAS (hidden system which below average but certified pilots could not handle) is just showing us the future where we are going.

Originally Posted by bill fly View Post
A doctor or an architect doesn’t go through this process - has to prove him(her)self to stay in business in other ways...
Everybody goes through the process, including (or especially) doctors. But yes, some fields have wider variations that others.

Originally Posted by bill fly View Post
So an aircraft designer has the right to expect a certain level of skill.
I would argue they need to support any pilot with a valid license. If they think licensed pilots are not good enough for their machines, we have a big, big problem.

Originally Posted by bill fly View Post

I seem to remember in my manual, that Boeing were pretty clear on the skill tests their pilots were expected to pass. That needs to be borne in mind when using terms like “average”.
Boeing can only dictate the minimum. Average is outside of their control. That said, do they specify that "a pilot should at minimum be able to identify a problem with an undocumented system, while flying close to the ground at high speed with stick shaker, no indication that AoA diasagree, and trim behaving like it's just the opposite of STS but not quite runaway stab trim". Do they? No really, do they? We are talking about a minimum skill required here.

Originally Posted by bill fly View Post

On the other hand, a professional pilot has the right to expect a level of skill from the manufacturer. This includes honest self criticism such as is required of a professional pilot.
B
Originally Posted by bill fly View Post
Challenger didn't happen due to engineering skill problem. On the contrary, engineering told the managers exactly what the risk was. These problems are created by greed.
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Old 23rd May 2019, 12:13
  #83 (permalink)  
 
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Originally Posted by derjodel View Post
First of all, the picture above is not a scale, it's a distribution where 100 represents the average pilot. There will always, always be pilots who are below average and pilots who are above average. The question is, how below average is the worse commercial pilot currently flying (and how good is the best one on the opposite side).
An equally valid question would be why ability (at anything, not necessarily confined to piloting) should be assumed to follow a normal distribution (normal in the mathematical sense, i.e. symmetrical about the mean/median/mode).

It's perfectly possible that the ability distribution is actually skewed, in other words the peak isn't halfway between the two extremes, so that for example there could be a concentration of pilots towards the upper end of the ability scale.

Or, perish the thought, the lower end.
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Old 23rd May 2019, 12:31
  #84 (permalink)  
 
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Originally Posted by DaveReidUK View Post

It's perfectly possible that the ability distribution is actually skewed, in other words the peak isn't halfway between the two extremes, so that for example there could be a concentration of pilots towards the upper end of the ability scale.

Or, perish the thought, the lower end.
Possible with a small number.
With a sufficient number of thousands of individuals, the distribution always seems to more or less follow the above curve, whatever the criteria, be it body height, fish size, driving or piloting "abilities".

The notion that some professional pilots could not be up to "average" may seem a bit disturbing, and yet we all know some colleagues that are "outstanding". And unfortunately, some others are not as good, so this de facto creates a distribution where some are "above average" and some are below...


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Old 23rd May 2019, 12:35
  #85 (permalink)  
 
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Originally Posted by tdracer View Post
Now, I'm not suggesting we're to the point where we can design the aircraft so we don't need pilots - that's still decades away. But when pilots become completely overwhelmed and demonstrate the inability to even remember to pull the throttles back so they don't overspeed when something goes wrong, it moves us one more step in that direction.
Interesting, I think that there are challenges remaining, but would expect to see fully autonomous aircraft as a more realistic proposition than genuinely fully autonomous cars. The technology will be there within a decade (about the same time as I will never have to fly again I hope).

However, Do I have the confidence in the implementation quality and regulatory enforcement which makes that technology actually safe ? . . . No chance.

There is a 'race to the bottom' in the software business which largely makes it fundamentally incompatible with the creation of high end safety critical solutions.

The more complex and critical those systems are the more incompatible that approach becomes. I see it regularly in many industries and it is both concerning and somewhat eye opening when you see what is really going on under the skin, as may be becoming apparent with this aircraft.
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Old 23rd May 2019, 13:00
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Originally Posted by DaveReidUK View Post
An equally valid question would be why ability (at anything, not necessarily confined to piloting) should be assumed to follow a normal distribution (normal in the mathematical sense, i.e. symmetrical about the mean/median/mode).

It's perfectly possible that the ability distribution is actually skewed, in other words the peak isn't halfway between the two extremes, so that for example there could be a concentration of pilots towards the upper end of the ability scale.

Or, perish the thought, the lower end.
Well, first of all, it doesn't really matter. The whole argument still stands, even if the distribution is skewed. Worse even, if it's skewed, then you have either some really, really bad pilots out there, or most pilots are below average, with a few aces flying around. Which one would you choose ;-)?

But in reality, it's very likely very close to normal. Take an example: how is the height of NBA players distributed? We pick the best, tallest athletes from the whole population, for sure they will all be best of the best, right? There are just 500 NBA players, out of the population of 300,000,000, that's top 0.000167%. For sure their height can't be normally distributed??

Well, spoiler alert, their height is basically normally distributed.

Ok, actually this is showing % of minutes played by different heights, so one could expect it to be even more skewed, but it's not.

And that's just 500 players. There are 600x more airline pilots, and with the sample size like that, the distribution is going to be normal.
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Old 23rd May 2019, 15:01
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Originally Posted by derjodel View Post
And that's just 500 players. There are 600x more airline pilots, and with the sample size like that, the distribution is going to be normal.
OK, I must have missed the lesson in statistics class demonstrating that large distributions are always normal.

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Old 23rd May 2019, 15:22
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Originally Posted by DaveReidUK View Post
OK, I must have missed the lesson in statistics class demonstrating that large distributions are always normal.
You are trying to make the whole arument invalid on a premise of "pilot skills don't necesseraly follow normal distribution.

1. How exactly does the type of distribution make my argument invalid? Plug in whatever you like, it's still the same.

2. Yes, indeed you might have missed the Central Limit Theorem. And because skill is sum of many different factors, the pilot skill is even more likely to be normally distributed.
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Old 23rd May 2019, 15:45
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I am not a pilot, but I am a Chartered Engineer, Chartered Statistician, a Chartered IT Professional, a European Engineer, and a Fellow of the Royal Statistical Society, with a Doctorate in Operational Research and Mathematical Statistics.

Not all natural distributions are Normal. However, very many are, because of the Central Limit Theorem. In essence, if a physical measurement is the sum of smaller figures, it is very likely to be Normal. That's why heights of people are approximately Normal, IQs are roughly Normal, etc.
It would be very surprising if the performance of pilots differed much from a Normal distribution.
A Normal (or Gaussian) Distribution is entirely described by its mean and variance. So, unless the distribution of performance of pilots is very unusual (such as a Laplace Distribution), the only relevant features of the distribution of pilot performance will be the mean (or average) and the variance (which determines how many are in the "tails" and how long the "tails" are).
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Old 23rd May 2019, 15:51
  #90 (permalink)  

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The word average (skilled) pilot should be avoided for the purpose of this discussion. If we are true to the mathematical meaning, adding even a small number of extremely well proficient people to a group, the previously "average" pilots of that group become less-than-average.

Less than average skilled sounds like "not competent enough to fly an aircraft designed for an average pilot". Which itself is an element of the debate, thus the word "average" makes a big mess of everything here.

My suggestion is that "the average pilot" in the certification realm means "any pilot who passed the licence proficiency criteria with at least bit of a margin, is able to achieve that or better performance continuously (as his experience builds but memory fades), and is not having a bad day"
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Old 23rd May 2019, 15:53
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Recent discussions have revolved around the man and machine. The inconclusive (different) views reflect the difficulty in defining the problem, together with the natural human dislike of uncertainty. These are further restricted in forum communication, how best to convey judgements with text, especially where these depend on the task being assessed and operating environment, each with a range of interpretations.

There are views of the man or machine, and then the ‘vague’ interface between them. Each attempts to quantify parameters of reliability and/or performance; similarly the concept of average seeks quantity, but most cases the real world the divisions are subjective - uncertain - qualitative judgement. (Skill is not a number, it’s a subjective rating). Numerical or statistical assessments are meaningless without first constraining the contributing parameters.

This is like an experiment judging human performance for a given task (detect trim runaway and act), but where the environment defining the situation is primarily determined by the test subject - the experiment is unbounded. We cannot measure what the crew perceived or ‘felt’ about the situation, or know what they knew - or recalled, or why they acted as they did.

All that might be concluded is that the performance of the single ‘entity’, the human and machine (humach?) in the circumstance was insufficient for the task. The balance of contributions in improving ‘humach’ capability is a judgement, best made within the guidelines of certification and the wide range of experience in that process.
The recent accidents suggest that the overall process for this judgement (certification, design, and test) was flawed; the resultant uncertainty in system failure could not be managed by ‘humach’.

The certification process is being reviewed, thus should identify technical and human aspects to be reassessed, as should be the resultant uncertainty from system failure.

We may not be able to judge any of the above without greater understanding of the original certification, the accident system failure, proposed modification, and most of all the associated justification.
With that, the subjective discussion in this forum and elsewhere could be founded on fact - reducing some of uncomfortable ‘uncertainty’ and need to resort to quantities to describe uncertainty.

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Old 23rd May 2019, 16:51
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Statistics

Sorry, I don’t buy that graph. Too convenient. If we have over 7 billion people in the world and just over 50% are in working age, and there are 300,000 odd pilots in the world, then there is one pilot per 14,000 people roughly - a small number, even if the figures are da-neben.
Let’s say there is a similar graph of 7 odd billion people. Where do you put these few pilots on it? And I am talking about selected airline employed professionals.
What do you measure on such a graph?
Intelligence? Co-ordination? Leadership? Team spirit? Drive? Fitness? Imagination?
All these factors bear on a pilot’s suitability as well as other, conflicting things such as:
Ability to concentrate on an item vs ability to keep the big picture
Ability to stick to procedure vs ability to throw away the rules and improvise
Ability to command vs ability to take advice
Ability to insist vs ability to be patient.
Ability to consider carefully vs ability to act fast
and many other conundrums which don’t mean you are especially clever - but suitable.
If you could quantify and measure all those qualities I very much doubt you would get a nice neat rounded peak for the general population as you would for an intelligence alone graph and even if you did, if you take a bunch of people out of it and scan them, the shape of the new graph would depend on where they were on the old one. Still a nice hill in the middle? I don’t think so.
Now about getting a licence - that is one small part of getting an airline job - one which you have to have but not one which will cause an airline to take you - they are looking for the items above.
So to design a machine for anyone who has managed to get a licence is not what is required. The operative word is professional. Design a machine for the pros and train them on it, then you will have safety.
Anyway the Jodel is a good ship - and as we know old men think there are lies, damn lies and statistics! ^_^
B
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Old 23rd May 2019, 17:29
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Originally Posted by derjodel View Post
You are trying to make the whole arument invalid on a premise of "pilot skills don't necesseraly follow normal distribution.

1. How exactly does the type of distribution make my argument invalid? Plug in whatever you like, it's still the same.

2. Yes, indeed you might have missed the Central Limit Theorem. And because skill is sum of many different factors, the pilot skill is even more likely to be normally distributed.
The question is how bad is the cutoff across the skill axis which is necessary in an emergency? Is your cloud really spherical or is it eccentric?

To become a *commercial* pilot you need ability to take orders, ability to learn, to do CRM, to be methodical etc etc. And a certain ability to fly the plane. And all these factors are tested for. But on the day HAL decides to take a vacation or turn hostile, you suddenly need grace under pressure, a capacity to retain situational awareness, an ability to hand fly the plane in a configuration which has *not* been trained for, a will to find some way to survive. See Sully.. The problem with the aircraft design may be that the designers assume that the pilots have been selected adequately because of the shape of the large distribution, and find out that the distribution of skills necessary in an emergency is actually a bell shaped but much sharper curve with few individuals matching the criteria necessary for survival.

Edmund
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Old 23rd May 2019, 17:32
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Originally Posted by FlightDetent View Post
The word average (skilled) pilot should be avoided for the purpose of this discussion. If we are true to the mathematical meaning, adding even a small number of extremely well proficient people to a group, the previously "average" pilots of that group become less-than-average.

Less than average skilled sounds like "not competent enough to fly an aircraft designed for an average pilot". Which itself is an element of the debate, thus the word "average" makes a big mess of everything here.

My suggestion is that "the average pilot" in the certification realm means "any pilot who passed the licence proficiency criteria with at least bit of a margin, is able to achieve that or better performance continuously (as his experience builds but memory fades), and is not having a bad day"
You are spot on. "Average" and "Subaverage" are usually interpreted very, very wrong. Not just by common people, even by people who really should know, like doctors (e.g., they would like to get rid of all subaverage tall kids, and go as far as even giving them growth hormones, producing just a smaller standard deviation and even more pressure on the small kids).

That's why I'm saying, designing airplanes for average pilot is very, very bad idea. Planes need to be designed for any certified pilot. And to make discussion clearer, perhaps it would be good idea to stick to those terms.

Because once you accept that planes must be designed for all certified pilots, then you can not, by definition, blame pilots to not react properly, specially in this situation.

It's actually the other way around - this crash is giving us a data point how a certain crew of certified pilots reacted in under specific circumstances. Actually we have a few more data points: penultimate Lion Air crash, ultimate Lion Air crash and ET crash. All are certified pilots. They reacted differently. Was the system designed to accommodate any certified crew?

And I'll go further and ask: isn't it the fact that the crew can not be responsible. Either they should not have been cleared to fly (e.g. stripped of their license, fail the MAX rating). Either they meet the minimums or they don't. If they don't and they still got licensed, it's not their fault. It's the regulator's. If they crashed because the plane was not flyable by any certified crew, it's boeing's fault.

The crew could only be at fault if they were under influence, if they cheated to pass the tests or hide any medical conditions etc...
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Old 23rd May 2019, 18:20
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d.j., your last paragraphs are missing the case of a properly qualified and competent pilot severely underperforming on a certain occasion. At this point, I am not connecting any dots to the MAX incidents and crashes as far as the crew performance goes, though a general remark that a poorly designed and implemented aircraft system (such as the MCAS on the MAX) will tip the scales.
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Old 23rd May 2019, 19:19
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Originally Posted by compiforce View Post
I am not a pilot, but I am a Chartered Engineer, Chartered Statistician, a Chartered IT Professional, a European Engineer, and a Fellow of the Royal Statistical Society, with a Doctorate in Operational Research and Mathematical Statistics.

Not all natural distributions are Normal. However, very many are, because of the Central Limit Theorem. In essence, if a physical measurement is the sum of smaller figures, it is very likely to be Normal. That's why heights of people are approximately Normal, IQs are roughly Normal, etc.
It would be very surprising if the performance of pilots differed much from a Normal distribution.
A Normal (or Gaussian) Distribution is entirely described by its mean and variance. So, unless the distribution of performance of pilots is very unusual (such as a Laplace Distribution), the only relevant features of the distribution of pilot performance will be the mean (or average) and the variance (which determines how many are in the "tails" and how long the "tails" are).
Q: If the average applicant scores 100 points on the pilot qualification test, made up of theoretical questions, and a simulator check, you say they should probably normally distributed. Lets say 60 % score between 90 and a 110 points, and the airlines only hire the pilots with over 90 points. With the 20% percent who didn't cut it missing, wouldn't the resulting curve be non-normally distributed? (and seeing hiring rates around 50% at interviews makes me think the skewing would be worse)

Had statistics class in college about 3 decades ago.....
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Old 23rd May 2019, 19:24
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Statistics are used by most people - especially politicians - just as drunks use lamp posts:-

... more for support than for the light they shed!
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Old 23rd May 2019, 19:31
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Originally Posted by derjodel View Post
That's why I'm saying, designing airplanes for average pilot is very, very bad idea. Planes need to be designed for any certified pilot. And to make discussion clearer, perhaps it would be good idea to stick to those terms.

Because once you accept that planes must be designed for all certified pilots, then you can not, by definition, blame pilots to not react properly, specially in this situation.

It's actually the other way around - this crash is giving us a data point how a certain crew of certified pilots reacted in under specific circumstances. Actually we have a few more data points: penultimate Lion Air crash, ultimate Lion Air crash and ET crash. All are certified pilots. They reacted differently. Was the system designed to accommodate any certified crew?

And I'll go further and ask: isn't it the fact that the crew can not be responsible. Either they should not have been cleared to fly (e.g. stripped of their license, fail the MAX rating). Either they meet the minimums or they don't. If they don't and they still got licensed, it's not their fault. It's the regulator's. If they crashed because the plane was not flyable by any certified crew, it's boeing's fault.

The crew could only be at fault if they were under influence, if they cheated to pass the tests or hide any medical conditions etc...
Excellent point, and excellent post !

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Old 24th May 2019, 06:03
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Originally Posted by hans brinker View Post
Q: If the average applicant scores 100 points on the pilot qualification test, made up of theoretical questions, and a simulator check, you say they should probably normally distributed. Lets say 60 % score between 90 and a 110 points, and the airlines only hire the pilots with over 90 points. With the 20% percent who didn't cut it missing, wouldn't the resulting curve be non-normally distributed? (and seeing hiring rates around 50% at interviews makes me think the skewing would be worse)

Had statistics class in college about 3 decades ago.....
Now consider that every airline has a different hiring process leading to a different cutoff. Maybe the cutoffs are normally distributed across the world..
You could also think about how consistent such a cutoff would be implemented, probably the hiring decision also depends on non-piloting factors.
In the end, the reason a pilot is given a license is because it is thought he is able to fly a plane. Obviously this needs to be consistent with what is required to actually do it, or there is a problem.
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Old 24th May 2019, 11:13
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Originally Posted by TehDehZeh View Post
In the end, the reason a pilot is given a license is because it is thought he is able to fly a plane. Obviously this needs to be consistent with what is required to actually do it, or there is a problem.
If you want the statistical argument to work in your favor, then it is important that both pilots in the cockpit meet these standards. That way you have a greater chance that one of them will be up to the task on any given day.
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