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Simple explanations of how to do Spearman Rank & Standard Deviation Please? watch

1. Just wondering if someone could explain how to do the Spearman Rank and Standard Deviation techniques in the simplest way possible?
2. Here's standard deviation:

34 45 56 23 79
(If you don't, and you start with a frequency table or something, let me know because you have to do different stuff for that!)

Square each number:
1156 2025 3136 529 6241

Now add all of the above together:
13087

And then divide how many there are:
2617.4

Moving on, now find the mean average of the original data (add them and divide by number of them):
47.4

Square it:
2246.76

Now take this number (2246.76) from the number we calculated before (2617.4) to get:
370.64

And finally, square root it:
19.252 (to 5.s.f.)

So:

Square
Divide by n

Average of original data
Square
Take
Root
Omg i just found the standard deviation!

Spoiler:
Show
If you can't remember which one to take from which on the "Take" step, then just think it's the one which gives a positive answer!
3. (Original post by Lou Reed)
They're both long-winded and boring to calculate, so no simple ways really.

For SD, i remember it as "sum of x squared over n", that's not all you do, here are the steps for a frequency table;
- square x to get x^2
- times frequency by corresponding x^2
- sum this
- divide by n
- minus the mean squared (i'm sure you know how to work out mean)
- square root it

For SR, the equation is really self-explanatory:

- find differences between the data
- square them
- sum them
- times by 6
- divide answer by (n(n^2 - 1))
- take answer away from 1

Does that help?
Seems to, just give me a bit to get my head round it lol.
4. (Original post by placenta medicae talpae)
Here's standard deviation:

34 45 56 23 79
(If you don't, and you start with a frequency table or something, let me know because you have to do different stuff for that!)

Square each number:
1156 2025 3136 529 6241

Now add all of the above together:
13087

And then divide how many there are:
2617.4

Remember this number!
Write it down or something

Moving on, now find the mean of the original data (add them and divide by number of them):
47.4

Square it:
2246.76

Now take this number (2246.76) from the number we calculated before (2617.4) to get:
370.64

And finally, square root it:
19.252 (to 5.s.f.)
Nice explanation

How would I calculate it for data on a frequency table then?
5. (Original post by sandeep90)
Seems to, just give me a bit to get my head round it lol.
Oh, erm, about this one - it's important that it's the ranks which have to be considered, rather than the actual values!
6. (Original post by sandeep90)
Nice explanation

How would I calculate it for data on a frequency table then?
Cheers - I edited it a bit, so it's much clearer now

To be honest, the formula is pretty much the same:
I just think of it as "stick an f before the x".

It is now:

Spoiler:
Show
If you prefer the alternative formula, then instead of being:

It is now:

And here, f.x^2 is the value representing a class, squared, and then timesed by the frequency of that class - how many values lie therein.
I appreciate that might be a little vague; let me know if it needs to be clarified.

I think that (surprisingly) the hardest bit of this is remembering how to find the mean from the frequency table!

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