Help me pleeeeeeaaaaase

[Harriet]

Hi this is gonna sound a little odd and radnom, but anyway.

My maths coursework is due in tomorrow and I got told today that it has to include standard deviation and Spearman's Rank of Coefficiancy (or something like that). Now, I know how to do standard deviation but I have NO idea what it means or shows, and I have absolutely no idea what the rank thing is or how to do it.

PLEASE somebody understand what I'm going on about and help me...if I don't hand this in tomorrow I lose 25% of my final Statistics GCSE mark.

[Poison Ivy]

here you go! this might help! I'm afraid I can't remember any of that stuff, I dropped maths and forgot everything as soon as I could!!! good luck!

http://www.bbc.co.uk/schools/gcsebitesize/maths/

[Claire]

I can give you a rough clue about what Standard Deviation means....

Pretend you have to work out the mean of a group of figures - let's imagine that the mean is 100.

You could get a mean of 100 from a group of numbers that were all very close to 100 - eg 98, 100, and 102 would give you a mean of 100.

Or - you could get a mean of 100 from some much more widely spread numbers - maybe 3, 100 and 197.

When you calculate a mean, the standard deviation gives you a measure of whether the numbers you used were widely spread out, or all clustered together close to the mean. A small SD means a narrow spread and a larger one means the numbers are much more spread out.

Hope that gets you started. I seem to think Fiona_1984 was doing a maths degree, (or that maths was a part of her degree at least) so hopefully she will wander by and be able to help a bit more!

[Harriet]

Thanks for the help :)
Ok, well for one of my questions my mean is 11-15 (it's grouped data) and the standard deviation is 32.4......does that make sense? That number just looks completely random, and I'm sure I've done all the calculations right........

*Confused*

[Royal Rother]

Give us the whole question Harriet.

[Harriet]

Never mind, have completely given up on the whole thing. This is what I put in and hoped for the best.

The standard deviation for the Year 7 is 32.4, and for Year 10 it is 16.51. Theoretically, this should mean that the Year 7 data is more widely spread, however my box and whisker plots show that the Year 10 data is more widely spread. I double checked all my calculations and cannot see what went wrong.

And of course rambled on a lot more like I know what's going on....and drew a compicated diagram and labeled everything so it looks all impressive.

[Opal]

Sorry - didn't find this before or I would have helped! As far as I remember from GCSE courseworks you get a lot of credit for workings - it's not all about getting the right answer. So I'm guessing if you went wrong somewhere but when you double checked you got the same wrong answer you probably only made one error. Also most exam boards do ECF (error carried forward) so you'll still get credit for the stuff you did after that error if your method is right!

Hope that makes you feel better about it! :)