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March 29, 2024, 09:18:34 am

Author Topic: Standard Math Q+A Thread  (Read 181140 times)  Share 

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dani01

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Re: Standard Math Q+A Thread
« Reply #660 on: August 06, 2019, 05:24:13 pm »
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Hi I'm having a bit of trouble wrapping my head around percentage error/measurement type questions (I know they are practically easy) but for example what would be the absolute error of the number 5.54mm. the formula sheet has 1/2 x precision but how do I find the precision? is it just .05 and then i half that to find the absolute error. so then if i have a number 7.89 the absolute error is the exact same? i think that is what I don't understand.
I get how to find the percentage error of the number but when I type it in to my calculator how do I know where to round off the percentage?

Hope this all makes sense    :) :)

RuiAce

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Re: Standard Math Q+A Thread
« Reply #661 on: August 06, 2019, 05:53:36 pm »
+1
Hi I'm having a bit of trouble wrapping my head around percentage error/measurement type questions (I know they are practically easy) but for example what would be the absolute error of the number 5.54mm. the formula sheet has 1/2 x precision but how do I find the precision? is it just .05 and then i half that to find the absolute error. so then if i have a number 7.89 the absolute error is the exact same? i think that is what I don't understand.
I get how to find the percentage error of the number but when I type it in to my calculator how do I know where to round off the percentage?

Hope this all makes sense    :) :)
The precision is basically just how far you go with decimal points. If your measurement is 5.54mm, then they are precise up to the nearest 0.01mm. So the absolute error is then one half of this, i.e. 0.005mm.

With 7.89, sure if you assume that it's also measured in mm. If it were in cm, then your absolute error would be 0.005cm.

I think you get told how far to round with your percentage error.
« Last Edit: August 06, 2019, 05:59:45 pm by RuiAce »

dani01

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Re: Standard Math Q+A Thread
« Reply #662 on: August 11, 2019, 03:08:42 pm »
+1
I've been doing some past papers and questions which always come up are those with combinations etc. Was this part of the old syllabus or do I have to know this because I have never done these in class or seen the formulas which are shown in the answers.

Mia-lexa

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Re: Standard Math Q+A Thread
« Reply #663 on: September 29, 2019, 01:35:13 pm »
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I've been doing some past papers and questions which always come up are those with combinations etc. Was this part of the old syllabus or do I have to know this because I have never done these in class or seen the formulas which are shown in the answers.

I think you're referring to probability? For example, you would find questions like: 'A bag contained 4 blue marbles, 3 red marbles and 2 green marbles. If Bob drew one marble and then drew another one. What is the probability that he will draw two marbles of the same colour?'
If this is the type of question you are talking about and you are having trouble understanding it or solving it, I would recommend revising it and asking for help from your math teachers. There are also papers you can find online with worked examples that can help you work closely on a specific subject as such. Probability is part of our current syllabus so it would definitely be worth revising before your final exams. Good luck!  ;)
« Last Edit: September 29, 2019, 01:51:53 pm by Mia-lexa »

dani01

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Re: Standard Math Q+A Thread
« Reply #664 on: October 01, 2019, 11:08:33 am »
+1
I think you're referring to probability? For example, you would find questions like: 'A bag contained 4 blue marbles, 3 red marbles and 2 green marbles. If Bob drew one marble and then drew another one. What is the probability that he will draw two marbles of the same colour?'
If this is the type of question you are talking about and you are having trouble understanding it or solving it, I would recommend revising it and asking for help from your math teachers. There are also papers you can find online with worked examples that can help you work closely on a specific subject as such. Probability is part of our current syllabus so it would definitely be worth revising before your final exams. Good luck!  ;)

Hey its all good I was talking about something called permutations and I checked with my teacher a while back and Its nothing I've got to worry about since it is part of the old sylllabus! thanks though

LoneWolf

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Re: Standard Math Q+A Thread
« Reply #665 on: January 07, 2020, 08:07:17 am »
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Hey People,

Just a quicky.

Should i use 'sample' or 'population' standard deviation when they just ask for 'standard deviation'?
Also, it may be beneficial if some1 could tell me the difference!

Thanks everybody
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RuiAce

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Re: Standard Math Q+A Thread
« Reply #666 on: January 07, 2020, 04:20:29 pm »
+2
Hey People,

Just a quicky.

Should i use 'sample' or 'population' standard deviation when they just ask for 'standard deviation'?
Also, it may be beneficial if some1 could tell me the difference!

Thanks everybody
The difference is really in what a sample is. The population standard deviation is the actual standard deviation. 'Population' refers to every object that you have.

A 'sample' is when you take only some of the objects out of the entire population. It's important because, in practice statisticians are not going to be able to survey everyone in the population. Only a small bunch will respond, and they are the sample. But the sample has to be used to deduce all statistical conclusions.

The sample standard deviation is used when you're interested in the SD of a sample. (In the real world, it's used to estimate the population standard deviation.)

I asked the standard math team and they've told me that generally you should use the population SD. Presumably, this would be because you're usually given information about the entire population. Or at the very least, from my understanding, you should assume that's the case when you're given no further info.

LoneWolf

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Re: Standard Math Q+A Thread
« Reply #667 on: January 07, 2020, 09:03:09 pm »
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Ripper thanks RuiAce

So helpful to have another POC when your school teacher doesnt respond ;D
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LoneWolf

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Re: Standard Math Q+A Thread
« Reply #668 on: January 08, 2020, 10:16:41 am »
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Hello People,

Does anyone know how to activate the pearsons correlation coefficient mode on a CASIO fx-82AU PLUS II?
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LoneWolf

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Re: Standard Math Q+A Thread
« Reply #669 on: January 08, 2020, 10:45:54 am »
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Have since worked it out.

1. Turn on right stat mode
 - Mode, 2:stat, 2:A+BCX
2. Enter Data (independent variable x-axis)
- Enter data, AC.
3. Extract Data
- Shift, 1:Stat, 5:Reg, 3:r
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LoneWolf

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Re: Standard Math Q+A Thread
« Reply #670 on: January 08, 2020, 12:12:12 pm »
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Another question  ;D ;D ;D

Why doesn't correlation imply causation?
It is simple but i am getting very muddled! i.e. why, doesnt the data prove just that?
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RuiAce

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Re: Standard Math Q+A Thread
« Reply #671 on: January 08, 2020, 05:08:11 pm »
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Another question  ;D ;D ;D

Why doesn't correlation imply causation?
It is simple but i am getting very muddled! i.e. why, doesnt the data prove just that?
There's actually a Wikipedia article on this. It's a very famous statistical concept.

To summarise it though, the WIkipedia article presents several counter-examples to disprove that "correlation must imply causation". The Wikipedia article also suggests reasons why there may be no causation between the two variables you're modelling,

If you're not bothered to read the entire Wikipedia page, this is perhaps one of the examples I feel illustrates the point the most..

Quote
As ice cream sales increase, the rate of drowning deaths increases sharply.
Therefore, ice cream consumption causes drowning.

This example fails to recognize the importance of time of year and temperature to ice cream sales. Ice cream is sold during the hot summer months at a much greater rate than during colder times, and it is during these hot summer months that people are more likely to engage in activities involving water, such as swimming. The increased drowning deaths are simply caused by more exposure to water-based activities, not ice cream. The stated conclusion is false.

In short, here, the two variables seemed highly correlated, but not because one caused the other. But rather, there was a hidden third variable that was causing both to increase.

The Wikipedia article shows that in general, this might not be the only reason that disproves "correlation implies causation". But this reason seems to be the easiest to understand, in my opinion.
« Last Edit: January 08, 2020, 05:11:00 pm by RuiAce »

LoneWolf

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Re: Standard Math Q+A Thread
« Reply #672 on: January 08, 2020, 08:14:22 pm »
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Ah smashing.
Thanks again.
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LoneWolf

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Re: Standard Math Q+A Thread
« Reply #673 on: January 23, 2020, 08:25:52 am »
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Another One' 8)

Is hamiltonian graphs part of the syllabus, it is in my cambridge textbook (genny) and im not sure if its worth stdying. it says ENRICHMENT.

THANKS
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RuiAce

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Re: Standard Math Q+A Thread
« Reply #674 on: January 23, 2020, 10:14:37 am »
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You can see from the syllabus that it is NOT in the syllabus.

Your teacher may be able to bend the grounds a little and put it inside an assignment task. But it is not in the syllabus and thus should never appear in an exam.