Velocity Reviews > Re: OT: London Cops seem to have a \$54K time problem

# Re: OT: London Cops seem to have a \$54K time problem

Ray Fischer
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Posts: n/a

 01-23-2012
Eric Stevens <(E-Mail Removed)> wrote:
>On 22 Jan 2012 23:13:43 GMT, http://www.velocityreviews.com/forums/(E-Mail Removed) (Ray Fischer) wrote:
>
>>PeterN <(E-Mail Removed)> wrote:
>>>On 1/22/2012 4:06 PM, Ray Fischer wrote:
>>>> PeterN<(E-Mail Removed)> wrote:
>>>>> On 1/22/2012 12:03 PM, Alan Browne wrote:
>>>>>> On 2012-01-22 11:26 , tony cooper wrote:
>>>>>>> "Impossible" was not a word chosen wisely. In this area, there are
>>>>>>> magnet schools for the gifted. I would imagine that all of the
>>>>>>> students in a school such as this would be above-average in
>>>>>>> intelligence for their age group.
>>>>>>
>>>>>> Correct. However the context of the statement (that Pete supplied) is in
>>>>>> the general school system.
>>>>>>
>>>>>> Quibble: it's not about 'intelligence' but performance and test results.
>>>>>
>>>>> My quibble:
>>>>>
>>>>> Assume a student population of 100.
>>>>> 75 A
>>>>> 25 c
>>>>>
>>>>> Obviously more than half the students will be above average.
>>>>
>>>> Nope. The average is an A. No students are above average and
>>>> many are below average.
>>>>
>>>> The math:
>>>> A = 4
>>>> C = 2
>>>> (75 * 4) + (25 * 2) = 350
>>>> 350 / 100 = 3.5 = A (rounded to the nearest letter grade)
>>>
>>>You didn't account for compensation for skewed curves.

>>
>>I was pointing out the fallacy of depending on rounded values.
>>By definition, you cannot have more than half of the students
>>score above average.

>
>Umm - you can you know.
>
>52 52 52 53 53 55 59 52 52 25
>
>10 students with an average of 45.

--
Ray Fischer | None are more hopelessly enslaved than those who falsely believe they are free.
(E-Mail Removed) | Goethe

Ray Fischer
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Posts: n/a

 01-23-2012
Eric Stevens <(E-Mail Removed)> wrote:
>On 23 Jan 2012 07:29:07 GMT, (E-Mail Removed) (Ray Fischer) wrote:
>
>>Eric Stevens <(E-Mail Removed)> wrote:
>>>On 22 Jan 2012 23:13:43 GMT, (E-Mail Removed) (Ray Fischer) wrote:
>>>
>>>>PeterN <(E-Mail Removed)> wrote:
>>>>>On 1/22/2012 4:06 PM, Ray Fischer wrote:
>>>>>> PeterN<(E-Mail Removed)> wrote:
>>>>>>> On 1/22/2012 12:03 PM, Alan Browne wrote:
>>>>>>>> On 2012-01-22 11:26 , tony cooper wrote:
>>>>>>>>> "Impossible" was not a word chosen wisely. In this area, there are
>>>>>>>>> magnet schools for the gifted. I would imagine that all of the
>>>>>>>>> students in a school such as this would be above-average in
>>>>>>>>> intelligence for their age group.
>>>>>>>>
>>>>>>>> Correct. However the context of the statement (that Pete supplied) is in
>>>>>>>> the general school system.
>>>>>>>>
>>>>>>>> Quibble: it's not about 'intelligence' but performance and test results.
>>>>>>>
>>>>>>> My quibble:
>>>>>>>
>>>>>>> Assume a student population of 100.
>>>>>>> 75 A
>>>>>>> 25 c
>>>>>>>
>>>>>>> Obviously more than half the students will be above average.
>>>>>>
>>>>>> Nope. The average is an A. No students are above average and
>>>>>> many are below average.
>>>>>>
>>>>>> The math:
>>>>>> A = 4
>>>>>> C = 2
>>>>>> (75 * 4) + (25 * 2) = 350
>>>>>> 350 / 100 = 3.5 = A (rounded to the nearest letter grade)
>>>>>
>>>>>You didn't account for compensation for skewed curves.
>>>>
>>>>I was pointing out the fallacy of depending on rounded values.
>>>>By definition, you cannot have more than half of the students
>>>>score above average.
>>>
>>>Umm - you can you know.
>>>
>>>52 52 52 53 53 55 59 52 52 25
>>>
>>>10 students with an average of 45.

>>

>
>I realised that was wrong after I posted.

In more than one way.

>I'm the last one with 25. Knock off 5 marks for my mistake and the

You playing games by depending on rounding errors and too-small sample
sizes.

--
Ray Fischer | None are more hopelessly enslaved than those who falsely believe they are free.
(E-Mail Removed) | Goethe

PeterN
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Posts: n/a

 01-23-2012
On 1/23/2012 2:10 PM, Ray Fischer wrote:
> Eric Stevens<(E-Mail Removed)> wrote:
>> On 23 Jan 2012 07:29:07 GMT, (E-Mail Removed) (Ray Fischer) wrote:
>>
>>> Eric Stevens<(E-Mail Removed)> wrote:
>>>> On 22 Jan 2012 23:13:43 GMT, (E-Mail Removed) (Ray Fischer) wrote:
>>>>
>>>>> PeterN<(E-Mail Removed)> wrote:
>>>>>> On 1/22/2012 4:06 PM, Ray Fischer wrote:
>>>>>>> PeterN<(E-Mail Removed)> wrote:
>>>>>>>> On 1/22/2012 12:03 PM, Alan Browne wrote:
>>>>>>>>> On 2012-01-22 11:26 , tony cooper wrote:
>>>>>>>>>> "Impossible" was not a word chosen wisely. In this area, there are
>>>>>>>>>> magnet schools for the gifted. I would imagine that all of the
>>>>>>>>>> students in a school such as this would be above-average in
>>>>>>>>>> intelligence for their age group.
>>>>>>>>>
>>>>>>>>> Correct. However the context of the statement (that Pete supplied) is in
>>>>>>>>> the general school system.
>>>>>>>>>
>>>>>>>>> Quibble: it's not about 'intelligence' but performance and test results.
>>>>>>>>
>>>>>>>> My quibble:
>>>>>>>>
>>>>>>>> Assume a student population of 100.
>>>>>>>> 75 A
>>>>>>>> 25 c
>>>>>>>>
>>>>>>>> Obviously more than half the students will be above average.
>>>>>>>
>>>>>>> Nope. The average is an A. No students are above average and
>>>>>>> many are below average.
>>>>>>>
>>>>>>> The math:
>>>>>>> A = 4
>>>>>>> C = 2
>>>>>>> (75 * 4) + (25 * 2) = 350
>>>>>>> 350 / 100 = 3.5 = A (rounded to the nearest letter grade)
>>>>>>
>>>>>> You didn't account for compensation for skewed curves.
>>>>>
>>>>> I was pointing out the fallacy of depending on rounded values.
>>>>> By definition, you cannot have more than half of the students
>>>>> score above average.
>>>>
>>>> Umm - you can you know.
>>>>
>>>> 52 52 52 53 53 55 59 52 52 25
>>>>
>>>> 10 students with an average of 45.
>>>

>>
>> I realised that was wrong after I posted.

>
> In more than one way.
>
>> I'm the last one with 25. Knock off 5 marks for my mistake and the

>
> You playing games by depending on rounding errors and too-small sample
> sizes.
>

In my original example, the sample size equaled 100% of the population.
I posted it for reasons previously stated.

--
Peter

Pete A
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Posts: n/a

 01-23-2012
On 2012-01-23 19:10:28 +0000, Ray Fischer said:

> Eric Stevens <(E-Mail Removed)> wrote:
>> On 23 Jan 2012 07:29:07 GMT, (E-Mail Removed) (Ray Fischer) wrote:
>>
>>> Eric Stevens <(E-Mail Removed)> wrote:
>>>> On 22 Jan 2012 23:13:43 GMT, (E-Mail Removed) (Ray Fischer) wrote:
>>>>
>>>>> PeterN <(E-Mail Removed)> wrote:
>>>>>> On 1/22/2012 4:06 PM, Ray Fischer wrote:
>>>>>>> PeterN<(E-Mail Removed)> wrote:
>>>>>>>> On 1/22/2012 12:03 PM, Alan Browne wrote:
>>>>>>>>> On 2012-01-22 11:26 , tony cooper wrote:
>>>>>>>>>> "Impossible" was not a word chosen wisely. In this area, there are
>>>>>>>>>> magnet schools for the gifted. I would imagine that all of the
>>>>>>>>>> students in a school such as this would be above-average in
>>>>>>>>>> intelligence for their age group.
>>>>>>>>>
>>>>>>>>> Correct. However the context of the statement (that Pete supplied) is in
>>>>>>>>> the general school system.
>>>>>>>>>
>>>>>>>>> Quibble: it's not about 'intelligence' but performance and test results.
>>>>>>>>
>>>>>>>> My quibble:
>>>>>>>>
>>>>>>>> Assume a student population of 100.
>>>>>>>> 75 A
>>>>>>>> 25 c
>>>>>>>>
>>>>>>>> Obviously more than half the students will be above average.
>>>>>>>
>>>>>>> Nope. The average is an A. No students are above average and
>>>>>>> many are below average.
>>>>>>>
>>>>>>> The math:
>>>>>>> A = 4
>>>>>>> C = 2
>>>>>>> (75 * 4) + (25 * 2) = 350
>>>>>>> 350 / 100 = 3.5 = A (rounded to the nearest letter grade)
>>>>>>
>>>>>> You didn't account for compensation for skewed curves.
>>>>>
>>>>> I was pointing out the fallacy of depending on rounded values.
>>>>> By definition, you cannot have more than half of the students
>>>>> score above average.
>>>>
>>>> Umm - you can you know.
>>>>
>>>> 52 52 52 53 53 55 59 52 52 25
>>>>
>>>> 10 students with an average of 45.
>>>

>>
>> I realised that was wrong after I posted.

>
> In more than one way.
>
>> I'm the last one with 25. Knock off 5 marks for my mistake and the

>
> You playing games by depending on rounding errors and too-small sample
> sizes.

It's a completely valid dataset. It is the analysis of it that has lead
to the false claim that it proves more than half of the students score
above average.

The "average" value of a dataset is a single number that most typifies
the datapoints within it. Here's the dataset placed in order:

25 52 52 52 52 52 53 53 53 59

We can see by inspection that a suitable average is 52 or 53. Three
commonly-used methods of calculating the average are:

mean: 50.5
median: 52
mode: 52

The arithmetic mean (aka mean) has been influenced heavily by the
outlying datapoint of 25. An extreme example is:

100000 52 52 52 52 52 53 53 53 59

mean: 10048
median: 52.5
mode: 52

This time, it's completely obvious that the mean of 10048 does _not_
typify the values in the dataset

The median is a far better average for data with high varience because
it not only better typifies the dataset, it also prevents absurd
conclusions being drawn such as "all but one of the values is far below
average". The median is calculated such that no more than half of the
samples can be above average and no more than half can be below.

In the original dataset, with a median of 52, one data point is below
average, 4 are average, and 4 are above average.

In the second example, with a median of 52.5, half of the dataset is
below average, the other half is above.

The term "average" is often thought to imply only the arithmetic mean,
but this is a misnomer.

Bruce
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Posts: n/a

 01-27-2012
Doug McDonald <(E-Mail Removed)> wrote:

>On 1/26/2012 4:42 PM, Alan Browne wrote:
>
>>
>>> My assertion that 50% of the schools will always score below average is
>>> correct, regardless of the actual values.

>>
>> Don't let actual values get in the way, mighty inconvenient, wot.
>>
>>> If this is found not to be the
>>> case in practice, then the scoring method is flawed...

>>

>
>Actually it is wrong. Half the schools will score below the MEDIAN,
>not the average.
>
>Doug Nitpicker

Your nitpicking is misplaced because the term "average" can have more
than one meaning, including the median, arithmetic mean and mode.

http://en.wikipedia.org/wiki/Average

Richard
Guest
Posts: n/a

 01-27-2012
Bruce wrote:
> Doug McDonald <(E-Mail Removed)> wrote:
>
>> On 1/26/2012 4:42 PM, Alan Browne wrote:
>>
>>>
>>>> My assertion that 50% of the schools will always score below
>>>> average is correct, regardless of the actual values.
>>>
>>> Don't let actual values get in the way, mighty inconvenient, wot.
>>>
>>>> If this is found not to be the
>>>> case in practice, then the scoring method is flawed...
>>>

>>
>> Actually it is wrong. Half the schools will score below the MEDIAN,
>> not the average.
>>
>> Doug Nitpicker

>
>
> Your nitpicking is misplaced because the term "average" can have more
> than one meaning, including the median, arithmetic mean and mode.
>
> http://en.wikipedia.org/wiki/Average

Well, there ya go.
Is Doug a below average nitpicker?

Bruce
Guest
Posts: n/a

 01-27-2012
"Richard" <(E-Mail Removed)> wrote:
>Bruce wrote:
>> Doug McDonald <(E-Mail Removed)> wrote:
>>
>>> On 1/26/2012 4:42 PM, Alan Browne wrote:
>>>
>>>>
>>>>> My assertion that 50% of the schools will always score below
>>>>> average is correct, regardless of the actual values.
>>>>
>>>> Don't let actual values get in the way, mighty inconvenient, wot.
>>>>
>>>>> If this is found not to be the
>>>>> case in practice, then the scoring method is flawed...
>>>>
>>>
>>> Actually it is wrong. Half the schools will score below the MEDIAN,
>>> not the average.
>>>
>>> Doug Nitpicker

>>
>>
>> Your nitpicking is misplaced because the term "average" can have more
>> than one meaning, including the median, arithmetic mean and mode.
>>
>> http://en.wikipedia.org/wiki/Average

>
>Well, there ya go.
>Is Doug a below average nitpicker?
>

LOL!

No, he's an intelligent guy whose contributions here are almost always

David Dyer-Bennet
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Posts: n/a

 01-28-2012
Eric Stevens <(E-Mail Removed)> writes:

> On Fri, 27 Jan 2012 13:43:32 +0000, Bruce <(E-Mail Removed)>
> wrote:
>
>>Doug McDonald <(E-Mail Removed)> wrote:
>>
>>>On 1/26/2012 4:42 PM, Alan Browne wrote:
>>>
>>>>
>>>>> My assertion that 50% of the schools will always score below average is
>>>>> correct, regardless of the actual values.
>>>>
>>>> Don't let actual values get in the way, mighty inconvenient, wot.
>>>>
>>>>> If this is found not to be the
>>>>> case in practice, then the scoring method is flawed...
>>>>
>>>
>>>Actually it is wrong. Half the schools will score below the MEDIAN,
>>>not the average.
>>>
>>>Doug Nitpicker

>>
>>
>>Your nitpicking is misplaced because the term "average" can have more
>>than one meaning, including the median, arithmetic mean and mode.
>>
>>http://en.wikipedia.org/wiki/Average

>
> I wouldn't rely in Wikipedia for that. I have always been taught that
> 'average' was the 'arithmetic mean' and that the other measurements of
> central tendency were not the average.

Whereas I have always been taught that "average" is a vague term meaning
some indication of central tendency of a measurement, and that one of
those three is normally what's meant. And that you should be more
specific if appropriate.
--
David Dyer-Bennet, (E-Mail Removed); http://dd-b.net/
Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/
Photos: http://dd-b.net/photography/gallery/
Dragaera: http://dragaera.info

nick c
Guest
Posts: n/a

 01-28-2012
Eric Stevens wrote:
> On Fri, 27 Jan 2012 13:43:32 +0000, Bruce <(E-Mail Removed)>
> wrote:
>
>> Doug McDonald <(E-Mail Removed)> wrote:
>>
>>> On 1/26/2012 4:42 PM, Alan Browne wrote:
>>>
>>>>> My assertion that 50% of the schools will always score below average is
>>>>> correct, regardless of the actual values.
>>>> Don't let actual values get in the way, mighty inconvenient, wot.
>>>>
>>>>> If this is found not to be the
>>>>> case in practice, then the scoring method is flawed...
>>> Actually it is wrong. Half the schools will score below the MEDIAN,
>>> not the average.
>>>
>>> Doug Nitpicker

>>
>> Your nitpicking is misplaced because the term "average" can have more
>> than one meaning, including the median, arithmetic mean and mode.
>>
>> http://en.wikipedia.org/wiki/Average

>
> I wouldn't rely in Wikipedia for that. I have always been taught that
> 'average' was the 'arithmetic mean' and that the other measurements of
> central tendency were not the average.
>
> Regards,
>
> Eric Stevens

Oftentimes the median value of a series of numbers are viewed to mean
it's the average value of a series of numbers. In reality average and
median are not the same values.

For example: When a series of numbers such as -

13 10 20 19 and 15 are orderly rearranged to be 10 13 15 19 20 the
Median value of those numbers is 15 (15 is just the middle number of a
column of numbers) while the average value is 15.4 (the average value is
derived by means of a mathematical computation of a column of numbers).

It's easy to understand when the column consists of an odd number of
values. When there is and even number of values in a column the two
middle numbers become median values while the average value of a column
of numbers remains a calculated single value number.

It's the way of the West .... podner.

nick c
Guest
Posts: n/a

 01-28-2012
nick c wrote:
> Eric Stevens wrote:
>> On Fri, 27 Jan 2012 13:43:32 +0000, Bruce <(E-Mail Removed)>
>> wrote:
>>
>>> Doug McDonald <(E-Mail Removed)> wrote:
>>>
>>>> On 1/26/2012 4:42 PM, Alan Browne wrote:
>>>>
>>>>>> My assertion that 50% of the schools will always score below
>>>>>> average is
>>>>>> correct, regardless of the actual values.
>>>>> Don't let actual values get in the way, mighty inconvenient, wot.
>>>>>
>>>>>> If this is found not to be the
>>>>>> case in practice, then the scoring method is flawed...
>>>> Actually it is wrong. Half the schools will score below the MEDIAN,
>>>> not the average.
>>>>
>>>> Doug Nitpicker
>>>
>>> Your nitpicking is misplaced because the term "average" can have more
>>> than one meaning, including the median, arithmetic mean and mode.
>>>
>>> http://en.wikipedia.org/wiki/Average

>>
>> I wouldn't rely in Wikipedia for that. I have always been taught that
>> 'average' was the 'arithmetic mean' and that the other measurements of
>> central tendency were not the average.
>>
>> Regards,
>>
>> Eric Stevens

>
>
> Oftentimes the median value of a series of numbers are viewed to mean
> it's the average value of a series of numbers. In reality average and
> median are not the same values.
>
> For example: When a series of numbers such as -
>
> 13 10 20 19 and 15 are orderly rearranged to be 10 13 15 19 20 the
> Median value of those numbers is 15 (15 is just the middle number of a
> column of numbers) while the average value is 15.4 (the average value is
> derived by means of a mathematical computation of a column of numbers).
>
> It's easy to understand when the column consists of an odd number of
> values. When there is and even number of values in a column the two
> middle numbers become median values while the average value of a column
> of numbers remains a calculated single value number.
>
> It's the way of the West .... podner.
>

When confronted with an even numbered column of numbers, the two middle
numbers are Median values _that can be added together to obtain a single
Median value number_ .

Whew ......