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# Standard deviation watch

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1. (Original post by Notnek)
I’ve got 196 now by doing root 8486500-220 x (3590/220)/219
2. (Original post by Reece.W.J)
I’ve got 196 now by doing root 8486500-220 x (3590/220)/219
I don't understand your working. What formula are you using?
3. (Original post by Notnek)
I don't understand your working. What formula are you using?
The one in the formula booklet (probably the wrong one) and I might be putting the wrong numbers for the wrong thing such as X
4. (Original post by Reece.W.J)
The one in the formula booklet (probably the wrong one) and I might be putting the wrong numbers for the wrong thing such as X
If possible, can you please upload a screenshot of the formula you are looking at?
5. (Original post by Notnek)
If possible, can you please upload a screenshot of the formula you are looking at?
6. (Original post by Reece.W.J)
You seem to be getting mixed up with your formulas. In your working you have a table which includes e.g. f x MP. Where did this table come from? Are you following an example? Did your teacher give you a formula?

If you have time I recommend this video. It will explain the two main formulas.
7. (Original post by Notnek)
You seem to be getting mixed up with your formulas. In your working you have a table which includes e.g. f x MP. Where did this table come from? Are you following an example? Did your teacher give you a formula?

If you have time I recommend this video. It will explain the two main formulas.
Ik they should be called Xi and that but I just put midpoint on that. I’m aware of that formula and the other 2 but not sure how to fill it
8. (Original post by Reece.W.J)
Ik they should be called Xi and that but I just put midpoint on that. I’m aware of that formula and the other 2 but not sure how to fill it
I think you should start again and use this since your table indicates that you were trying to use this formula:

Firstly your column is wrong. means so you need to square the midpoint then multiply the result by the frequency.

It seems like you will need to ask your teacher to clarify this topic to you.
9. (Original post by Notnek)
I think you should start again and use this since your table indicates that you were trying to use this formula:

Firstly your column is wrong. means so you need to square the midpoint then multiply the result by the frequency.

It seems like you will need to ask your teacher to clarify this topic to you.
The whole class performed poorly on this topic so she’s going over it but wants us to fix the 3 questions in the test before the lesson. I’ll get back to you I think I’m getting closer
10. (Original post by Reece.W.J)
The whole class performed poorly on this topic so she’s going over it but wants us to fix the 3 questions in the test before the lesson. I’ll get back to you I think I’m getting closer
Okay great. I'm sorry if my earlier posts confused you - I wasn't sure what you knew/didn't know. Plus helping with stats questions on TSR is quite new for me
11. (Original post by Notnek)
Okay great. I'm sorry if my earlier posts confused you - I wasn't sure what you knew/didn't know. Plus helping with stats questions on TSR is quite new for me
Would you mind showing your working so I can learn to be able to do the next few? I’ve been doing this for like 1h now and I’m even getting maths error now
12. (Original post by Reece.W.J)
Would you mind showing your working so I can learn to be able to do the next few? I’ve been doing this for like 1h now and I’m even getting maths error now
Sorry I don't have time to write out a solution but I can guide you through this one.

Your column is wrong. So for the first entry of that column you need to do so 500 is the frst entry instead of 40000. Can you fix the rest of them then work out the total and post your working?
13. (Original post by Notnek)
Sorry I don't have time to write out a solution but I can guide you through this one.

Your column is wrong. So for the first entry of that column you need to do so 500 is the frst entry instead of 40000. Can you fix the rest of them then work out the total and post your working?
We were told to do f x mp then square answer. As you can see it makes a big difference
14. (Original post by Reece.W.J)
We were told to do f x mp then square answer. As you can see it makes a big difference
Can you please explain in words how you were taught to do all this? It doesn't matter if what you say is wrong.

I don't want to give you a method that is different to your teachers. If you want to use a method that I suggest then let me know.
15. (Original post by Notnek)
Can you please explain in words how you were taught to do all this? It doesn't matter if what you say is wrong.

I don't want to give you a method that is different to your teachers. If you want to use a method that I suggest then let me know.
Thanks for all your help but I think I’m going to have to give up
16. (Original post by Reece.W.J)
Thanks for all your help but I think I’m going to have to give up
I'll post a solution for your question. Give me a few mins.
17. (Original post by Reece.W.J)
Thanks for all your help but I think I’m going to have to give up

Spoiler:
Show

So

(For anyone wondering, full solutions are not normally allowed unless a thread has gone on for a while and the OP is still stuck.)
18. (Original post by Notnek)

So
Ok so I have that apart from the column on the right because we’ve definitely been told to square the answer of fx not f x x^2
19. (Original post by Reece.W.J)
Ok so I have that apart from the column on the right because we’ve definitely been told to square the answer of fx not f x x^2
I've shown you a method that will give you the answer. If your teacher is using a different method then please check with them.
20. (Original post by Notnek)
I've shown you a method that will give you the answer. If your teacher is using a different method then please check with them.
Ok thanks so much for your help

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Updated: October 11, 2017
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