# Maths!

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#21
(Original post by elpaw)
yes, always 68% of the data lies within + or - the sd of the mean

(assuming data is normally distributed)

right cool so the sd thingy answer is 24.7 say and the mean is 30, so 34% of the data will lie below the mean and 34% above showing that it is widely distributed? right? or if the sd thing is 7 say and the mean is 10 say, 34% will lie below 10 and 34% will lie above 10?
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16 years ago
#22
(Original post by XTinaA)
Paw, you said you did the remainder theorem by a way other than long division, how?
its too much to explain on here (because of the formatting) but i'll scan an example in later, and put it as an attachment.
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16 years ago
#23
right cool so the sd thingy answer is 24.7 say and the mean is 30, so 34% of the data will lie below the mean and 34% above showing that it is widely distributed? right? or if the sd thing is 7 say and the mean is 10 say, 34% will lie below 10 and 34% will lie above 10?
With SD=7 and mean=10, 68% of the data lies between 3 and 17.
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16 years ago
#24
(Original post by elpaw)
its too much to explain on here (because of the formatting) but i'll scan an example in later, and put it as an attachment.
Thanks a bunch.
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16 years ago
#25
right cool so the sd thingy answer is 24.7 say and the mean is 30, so 34% of the data will lie below the mean and 34% above showing that it is widely distributed? right? or if the sd thing is 7 say and the mean is 10 say, 34% will lie below 10 and 34% will lie above 10?
no, 68% will lie between the two bounds [mean-sd , mean+sd]

ie -sd<x<sd, and not as you said, -sd>x>sd
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#26
(Original post by XTinaA)
With SD=7 and mean=10, 68% of the data lies between 3 and 17.

ahhhhh i get it know! thanks soooooo much!! and also thanx for adding atachment!!!!
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#27
ahhhhh i get it know! thanks soooooo much!! and also thanx for adding atachment!!!!

Sorry 2 bug u guys again, but u no in the earlier exampl

sd = 7
mean = 10

so 68% of the data lies between 3 and 17.
What about the other 32% of the data? Where does that go?
thanx!
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#28
Sorry 2 bug u guys again, but u no in the earlier exampl

sd = 7
mean = 10

so 68% of the data lies between 3 and 17.
What about the other 32% of the data? Where does that go?
thanx!

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16 years ago
#29
Sorry 2 bug u guys again, but u no in the earlier exampl

sd = 7
mean = 10

so 68% of the data lies between 3 and 17.
What about the other 32% of the data? Where does that go?
thanx!
it goes below 3 and above 17
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#30
(Original post by elpaw)
it goes below 3 and above 17

yeah, so y do u only measure 68% of it?
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16 years ago
#31
yeah, so y do u only measure 68% of it?
you don't. it's just a mathematical fact that 68% of the data in a normal distribution falls withing an sd of the mean. noone suddenly woke up one day and said "i wonder what range 68% of the data falls in", the 68% came later, after the invention of the sd form.
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#32
(Original post by elpaw)
you don't. it's just a mathematical fact that 68% of the data in a normal distribution falls withing an sd of the mean. noone suddenly woke up one day and said "i wonder what range 68% of the data falls in", the 68% came later, after the invention of the sd form.

sorry 2 keep buggin u! just 1 more thing. wots the normal distribution?
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16 years ago
#33
sorry 2 keep buggin u! just 1 more thing. wots the normal distribution?
its as the name suggests, a normal distribution. itsthe distribution of heights and weights, or other physical quantities, which has teh bell shaped curve (attached)
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#34
(Original post by elpaw)
its as the name suggests, a normal distribution. itsthe distribution of heights and weights, or other physical quantities, which has teh bell shaped curve (attached)

so the other 32% would b people (if u were looking at heights) who were much taller or shorter (depending on which side of the mean they were) compared with the others? right?
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16 years ago
#35
so the other 32% would b people (if u were looking at heights) who were much taller or shorter (depending on which side of the mean they were) compared with the others? right?
yes, the other 32% would be shorter than (mean - sd) and taller than (mean+sd)
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#36
(Original post by elpaw)
yes, the other 32% would be shorter than (mean - sd) and taller than (mean+sd)

ahhhhh cool think i got it at last!!! thanx soooo much!!!
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