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 Post subject: Averages??
PostPosted: Wed Nov 21, 2007 5:14 pm 
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Joined: Mon Feb 20, 2006 1:29 pm
Posts: 1805
Location: Berkshire
Hi Guest55,

Could you please lend some of your expertise.

DS came home, extremely confused. In maths his teacher said...

Mean, mode,median and range are all types of average.
Parents are mathematically incorrect, when they say 'average' means 'mean'

Could you please clarify. Of course I've been guilty of exactly this. Have never considered mode, median and range as 'averages'

Thanks

BW


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 Post subject:
PostPosted: Wed Nov 21, 2007 5:38 pm 
http://en.wikipedia.org/wiki/Average

They're all averages in the strict mathematical sense of the word, but this story sounds to me like a pedantic Maths teacher splitting semantic hairs.


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 Post subject:
PostPosted: Wed Nov 21, 2007 5:52 pm 
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Sorry SM - the teacher is NOT being pedantic!

They are all 'averages' - so in an exam a question won't ask you to find the average but will ask for the mean, mode or median. In fact it might say 'which average is most appropriate to represent this data?'

The data might be 1,2,2,3,4,100

mode = 2 median = 2.5, mean = 112/6

Either the mode or median would be OK - the mean is 'distorted' by the large value.


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 Post subject:
PostPosted: Wed Nov 21, 2007 7:12 pm 
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Joined: Wed Oct 31, 2007 3:15 pm
Posts: 78
Hi all

I would like to add, as I understand, that they are all measures of 'average' but it is more appropriate to use one form of average rather than another at different times.

The mean, as shown above, can be a distorted average, but so can the median and the mode (and the range - although this is a measure of spread rather than an 'average'!).

Quite often students are asked to use an 'appropriate' average and state why they have used this measure of average as opposed to other measures.

Hope this helps!!!

P.S What does DS or DD mean? Thanks (no pun intended!)


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 Post subject: DD/DS
PostPosted: Wed Nov 21, 2007 8:08 pm 
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Joined: Wed May 09, 2007 2:09 pm
Posts: 875
Location: Solihull, West Midlands
I've always taken them as shortcuts for "dear daughter" "darling son" or any other epithet you might want to imagine for your offspring....

delightful
dreadful
diligent
demanding


etc


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 Post subject:
PostPosted: Wed Nov 21, 2007 8:12 pm 
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Joined: Mon Jun 18, 2007 2:32 pm
Posts: 6966
Location: East Kent
DS= darling (or dear) son, similarly dd = daughter.

I agree the teacher was not pedantic. There are different gategories of average. The common one is mode ie the most common.

I remeber an argument witha health visitor who was telling me off because my son eas below average...well someone has to be for there to BE an average! She meant below the median..of course I would never correct her :wink:


similarly David Blunkett's assertion that every child would be average or above! :shock:


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 Post subject:
PostPosted: Wed Nov 21, 2007 9:30 pm 
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Joined: Mon Feb 20, 2006 1:29 pm
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Location: Berkshire
Thankyou all for the information. Things have certainly changed at school.:?
Just surprised that they are teaching this at KS2. Especially as I haven't come across this sort of question in any paper we've done. They are always more explicit, and ask directly for the child to find the mean, median, or mode of the set of numbers they have shown. Never come across the 'appropriate average' type question.

Thanks

BW


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 Post subject:
PostPosted: Wed Nov 21, 2007 9:39 pm 
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I was talking about KS3 questions really - but able pupils might met this in Y6


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 Post subject:
PostPosted: Wed Nov 21, 2007 9:56 pm 
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Location: Berkshire
Guest55,

Thanks for clarifying, makes sense now :)

Have shown, DS this thread and explained as much as possible.

Thanks again,

BW


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 Post subject:
PostPosted: Wed Nov 21, 2007 9:59 pm 
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Joined: Sat Nov 17, 2007 8:55 pm
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Location: Bexley
Dear Bewildered. My eldest sons (Y8 and Y6) have been doing mean, mode and median since about Y5 (not just for 11+). I still struggle with definitions, and I'm not sure I entirely agree with some of the posts but my reliable maths dictionary states:

Mean = average
Median = the middle number of a set of numbers placed in order of size (the example given is in 32, 35, 36, 36, 38, 39, 42, 45, 47, 51, 51 the Median is 39)
Mode = in a set of numbers the Mode is the number which occurs most often (the example given is in 24, 27, 26, 28, 28, 27, 29, 32, 27 the mode is 27)

When preparing for 11+ exams I've found it useful to keep a list of terminology like this so that, a few days before the maths test, rather than do more practice, I can just check they remember the meaning. It would be a shame for a child to get a question wrong because they don't know the meaning of a word. 'Quotient' and 'Product' are other good examples. But I'm rambling now!!


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