# Maths GCSE coursework- Standard deviationWatch

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Thread starter 14 years ago
#1
Hi,

I am currently doing Maths GCSE coursework. I have never used standard deviation before but I have looked at the mark scheme and if you do use it you can get higher marks.

For the coursework I am comparing the length of words from a magazine and a newspaper. I have used a sample of 200 words for both the newspaper and the magazine samples.
The mean length of the words for the magazine= 4.17
Mean for the newspaper=4.76 letters

How would I go about calculating the standard deviation? I am totaly clueless, so please explain it as simply as pos. I seem to remember that it should be drawn on a graph.

Thanks loads
0
14 years ago
#2
It's been a long time since I did any stats so I'm not of much help in this area sorry.

However here is the Standard deviation formula explained. I hope this helps in some small way.

Remember that, Standard deviation=√(variance).
0
Thread starter 14 years ago
#3
(Original post by Slice'N'Dice)
It's been a long time since I did any stats so I'm not of much help in this area sorry.

However here is the Standard deviation formula explained. I hope this helps in some small way.

Remember that, Standard deviation=√(variance).
Hey thanks for your help, but I think that diagram is a bit beyond my mathematical abilities.
0
14 years ago
#4
(Original post by fivebyfive)
Hey thanks for your help, but I think that diagram is a bit beyond my mathematical abilities.
No problem. Sorry I can't be of much help to you.

I have found a couple of links for you about SD. Try having a read through these. These may help slightly.

Standard Deviation
Standard Deviation (2)

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Thread starter 14 years ago
#5
(Original post by Slice'N'Dice)
No problem. Sorry I can't be of much help to you.

I have found a couple of links for you about SD. Try having a read through these. These may help slightly.

Standard Deviation
Standard Deviation (2)

Thanks . The second website really helped, however am now stuck on what the result that i have actually means.
For the newspaper the SD=4.04
For the mag the SD=4.35

Can anyone explain what the SD is showing?

Thanks
0
14 years ago
#6
(Original post by fivebyfive)
Thanks . The second website really helped, however am now stuck on what the result that i have actually means.
For the newspaper the SD=4.04
For the mag the SD=4.35

Can anyone explain what the SD is showing?

Thanks
This kind of tells you what standard deviation shows.

Euclid
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Thread starter 14 years ago
#7
(Original post by Euclid)
This kind of tells you what standard deviation shows.

Euclid
Thanks I had a look at that site but am still not sure if my understanding of SD is correct?
Take the newspaper result; the SD is 4.04 (rounded off to 4) and the mean is 4.76 letters (rounded off to 5).
Therefore anything with a range of 4 letters difference in length from a word 5 letters in length is considered normal. I.e 2 letters up to 9 letters is considered normal, anything outside this range is not normal?
Still very puzzled about how this is suppose to fit on the graph. Can anyone offer any further assistance?

Thanks
0
Thread starter 14 years ago
#8
Can no one help? Or at least tell me if what i have already is correct? Otherwise my hour or so work on this going to be a waste of time

Thank you
0
14 years ago
#9
The standard deviation is basically the measure of how 'normal' your result is. If the mean for newspaper result is 5 and the SD is 4 then +/- 4 letters either way is still within the normal amount expected, (ie down to 1 and up to 9) You can plot this on a 'normal distribution graph'. If you have a look at this website there is an example garph on the left hand side,

http://www.stattucino.com/berrie/normal.html

you need to have the middle line as your mean value, the far left line as your mean - SD value and your far right line as the mean + SD value. Then the area enclosed by the two extreme lines is what is classed as 'normal.' You'll need to draw a graph for both sets of your results.

Hope this helps, don't worry if you don't understand all of it, try and put some in and even if you don't get all the higher marks you will probably get quite a few just for giving it a good go. If you need any more help post again and I'll give it a go!
0
Thread starter 14 years ago
#10
(Original post by Cathie86)
The standard deviation is basically the measure of how 'normal' your result is. If the mean for newspaper result is 5 and the SD is 4 then +/- 4 letters either way is still within the normal amount expected, (ie down to 1 and up to 9) You can plot this on a 'normal distribution graph'. If you have a look at this website there is an example garph on the left hand side,

http://www.stattucino.com/berrie/normal.html

you need to have the middle line as your mean value, the far left line as your mean - SD value and your far right line as the mean + SD value. Then the area enclosed by the two extreme lines is what is classed as 'normal.' You'll need to draw a graph for both sets of your results.

Hope this helps, don't worry if you don't understand all of it, try and put some in and even if you don't get all the higher marks you will probably get quite a few just for giving it a good go. If you need any more help post again and I'll give it a go!
Thanks for your help, that was just the explaination i needed.
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