Percentile Rank Question
January 31st, 2014 at 6:09:30 AM
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Simple question here. What is the highest percentile rank a person can have in a large population?
Here is the backstory. My brother said his daughter medically was ranked in "the 100th percentile" for something. I said that is impossible because you cannot be above 100% of everyone in the group because *you* are also in the group. He said the pediatrician said it that way.
Mathematically, what is the highest and lowest you can be? Assume a population of a million or more.
Here is the backstory. My brother said his daughter medically was ranked in "the 100th percentile" for something. I said that is impossible because you cannot be above 100% of everyone in the group because *you* are also in the group. He said the pediatrician said it that way.
Mathematically, what is the highest and lowest you can be? Assume a population of a million or more.
All animals are equal, but some are more equal than others
January 31st, 2014 at 6:33:33 AM
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99 and 1
January 31st, 2014 at 6:41:13 AM
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I think the formal convention is to allow for the 100th percentile, and that by definition this is the absolute highest value. One textbook I have allows for 0 to 100th percentiles.
When you are measuring something that doesn't have a bounded range, 0 is at - infinity and 100 is at + infinity, so in your case it is unreasonable to say they are in the 100th percentile: 99th is correct in this case.
When you are measuring something that doesn't have a bounded range, 0 is at - infinity and 100 is at + infinity, so in your case it is unreasonable to say they are in the 100th percentile: 99th is correct in this case.
Wisdom is the quality that keeps you out of situations where you would otherwise need it
January 31st, 2014 at 8:00:59 AM
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0th and 99th or 1st and 100th. There are 100 percentage points and you can view the measuring either way.
January 31st, 2014 at 8:22:15 AM
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At AT&T I was privy to employee appraisals. Amazing that 90% of employees were rated above average. WTF ?
Shed not for her
the bitter tear
Nor give the heart
to vain regret
Tis but the casket
that lies here,
The gem that filled it
Sparkles yet
January 31st, 2014 at 9:14:28 AM
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Quote: BuzzardAt AT&T I was privy to employee appraisals. Amazing that 90% of employees were rated above average. WTF ?
Sounds like Lake Wobegon
January 31st, 2014 at 9:15:21 AM
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Quote: BuzzardAmazing that 90% of employees were rated above average.
Just goes to show how those 10% of really, really bad employees screwed the average waaaaayyy down.
January 31st, 2014 at 9:16:40 AM
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Don't confuse average with median.Quote: BuzzardAmazing that 90% of employees were rated above average. WTF ?
Say one employee is rated 0 and nine are rated 10. The average is 9, and 90% are above.
Reperiet qui quaesiverit
January 31st, 2014 at 9:22:36 AM
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Quote: AZDuffmanSimple question here. What is the highest percentile rank a person can have in a large population?
Here is the backstory. My brother said his daughter medically was ranked in "the 100th percentile" for something. I said that is impossible because you cannot be above 100% of everyone in the group because *you* are also in the group. He said the pediatrician said it that way.
Mathematically, what is the highest and lowest you can be? Assume a population of a million or more.
The doc may have been using shorthand. Percentiles can also be specified which are fractional (eg 99.9th%). Rounding makes all of this confusing. It all depends on what level of significant figures is being used.
It is true that it is impossible for one element to be greater than all elements in a group when it is also a member of the set. However, it can be the least upper bound (if it is the maximum element). In the real world, this is mostly unimportant semantics. In math it can be rather useful to utilize these differences.
http://en.wikipedia.org/wiki/Supremum
January 31st, 2014 at 9:24:35 AM
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Quote: kubikulannDon't confuse average with median.
Say one employee is rated 0 and nine are rated 10. The average is 9, and 90% are above.
Every major company expects distributions of employee values which are more normal-ish. If there is any skewing to this distribution, they have long right tails.
January 31st, 2014 at 9:29:30 AM
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Their expectation is more or less ridiculous. These things are not supposed to show a Normal curve at all. In my wife's company, several people complained of their rating and were answered: sorry, if we rated you higher we would not respect the Normal curve.Quote: endermikeEvery major company expects distributions of employee values which are more normal-ish. If there is any skewing to this distribution, they have long right tails.
As this is related to the bonus earned, I think they don't care a nit at normality, they just want to screw us of our bonus.
Reperiet qui quaesiverit
January 31st, 2014 at 9:59:18 AM
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Quote: kubikulannTheir expectation is more or less ridiculous. These things are not supposed to show a Normal curve at all. In my wife's company, several people complained of their rating and were answered: sorry, if we rated you higher we would not respect the Normal curve.
As this is related to the bonus earned, I think they don't care a nit at normality, they just want to screw us of our bonus.
Theoretically, a company would seek to hire the best people, and all employees could be above average; the bad employee should be an anomaly. On the other hand, they could seek to hire the cheapest employees, many of whom would be less than average.
I heart Crystal Math.
January 31st, 2014 at 10:18:46 AM
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Management blew a gasket when I exposed their appraisal system. They had a point system that the employees did not know about.
5 categories you were ranked on. Then 4 columns " in need of improvement " "average " "above average " Always exceeds expectations "
If they wanted an employee to chase the carrot, then in 2 categories he was rated above average with comment similar to 3 in the
"always exceeds expectations " column. Sound like he might be on the promotion list, doesn't it ??
Except the secret ranking system was 1,2,3,6. So 3 points for each Above average. 6 points for always exceeds.
30 points max need, you need 25 to be on promotion list. Let's see, 2 X 3 = 6 3 x 6 = 18 6+18=24. LOL
Shades of RAZZLE LOL
5 categories you were ranked on. Then 4 columns " in need of improvement " "average " "above average " Always exceeds expectations "
If they wanted an employee to chase the carrot, then in 2 categories he was rated above average with comment similar to 3 in the
"always exceeds expectations " column. Sound like he might be on the promotion list, doesn't it ??
Except the secret ranking system was 1,2,3,6. So 3 points for each Above average. 6 points for always exceeds.
30 points max need, you need 25 to be on promotion list. Let's see, 2 X 3 = 6 3 x 6 = 18 6+18=24. LOL
Shades of RAZZLE LOL
Shed not for her
the bitter tear
Nor give the heart
to vain regret
Tis but the casket
that lies here,
The gem that filled it
Sparkles yet
January 31st, 2014 at 10:20:40 AM
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" On the other hand, they could seek to hire the cheapest employees, many of whom would be less than average. "
Not always true. Some companies trick employees into lower pay. Some companies will fire you if you let another employee see your paycheck.
Not always true. Some companies trick employees into lower pay. Some companies will fire you if you let another employee see your paycheck.
Shed not for her
the bitter tear
Nor give the heart
to vain regret
Tis but the casket
that lies here,
The gem that filled it
Sparkles yet
January 31st, 2014 at 6:21:16 PM
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Actually it's quite a smart idea. Say you graded people Very Good, Good, Average, Bad, Very Bad, it would make sense to give the impression that the average was "Average" whereas in reality most people were Good - it would make them feel good as well. I suspect other American companies might have used a similar tactic, certainly in the UK they tended to lead the way in using a kind of appraisal system to grade and hence reward employees.Quote: BuzzardAt AT&T I was privy to employee appraisals. Amazing that 90% of employees were rated above average. WTF ?
January 31st, 2014 at 6:56:30 PM
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My thought on most appraisals I got were that that was how management expected me to perform next year. And I would always tell them that and that I would do my best to meet their low expectations.
The appraisal is supposed to be an evaluation of your performance over the previous year. But almost always the only specific items were things that happened in the month or 2 prior. You know, when the supervisor was reminded appraisal were due next month.
And some supervisors rate everybody high, some rate everybody low, and in the leveling session, it all comes down to which supervisor has the most pull. I never signed an appraisal in 30+ years, despite threats of suspension. Why would I sign something I
did not agree with ?
The appraisal is supposed to be an evaluation of your performance over the previous year. But almost always the only specific items were things that happened in the month or 2 prior. You know, when the supervisor was reminded appraisal were due next month.
And some supervisors rate everybody high, some rate everybody low, and in the leveling session, it all comes down to which supervisor has the most pull. I never signed an appraisal in 30+ years, despite threats of suspension. Why would I sign something I
did not agree with ?
Shed not for her
the bitter tear
Nor give the heart
to vain regret
Tis but the casket
that lies here,
The gem that filled it
Sparkles yet
