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March 16, 2026, 01:58:34 am
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Author Topic: Question 3 Core - Standard Deviation  (Read 3792 times)  Share 

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ryanlp1

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Question 3 Core - Standard Deviation
« on: November 01, 2010, 05:47:27 pm »
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Hey could somebody please explain to me why the answer is B and NOT C ?

I still don't quite get it.

Thanks =]
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_avO

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Re: Question 3 Core - Standard Deviation
« Reply #1 on: November 01, 2010, 05:49:32 pm »
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Because you have to use the 68%/95%/99.7% rule (almost the same as range/8) and not range/4
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vexx

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Re: Question 3 Core - Standard Deviation
« Reply #2 on: November 01, 2010, 05:59:41 pm »
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Quote from: _avO on November 01, 2010, 05:49:32 pm
Because you have to use the 68%/95%/99.7% rule (almost the same as range/8) and not range/4

yeah, you find the amount of units to each side to give you within the 68%, or 34% on one side, and see that it was about 2, hence the SD is 2.
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kriptik

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Re: Question 3 Core - Standard Deviation
« Reply #3 on: November 01, 2010, 06:03:38 pm »
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if you got the standard deviation formula from essentials maths book, it is wrong. the formula should be (range)/6. i remember covering that section at the start of the year and my teacher told us to fix it.

and also there was a similar question  2001 exam 1 Q6. doing range/6 gives the right answer, but range/4 doesnt. might wanna check it out.
« Last Edit: November 01, 2010, 06:05:26 pm by kriptik »
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ZachCharge

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Re: Question 3 Core - Standard Deviation
« Reply #4 on: November 01, 2010, 06:12:15 pm »
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Wahahah, the only SD formula I found in MQ was the one used for S+L plots and I used one from bound notes here (which I hear came from essentials)...argh...so unfair...
« Last Edit: November 01, 2010, 06:28:13 pm by ZachCharge »
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Nads

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Re: Question 3 Core - Standard Deviation
« Reply #5 on: November 01, 2010, 06:32:37 pm »
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How come Core Q 1 was D? not E?
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ZachCharge

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Re: Question 3 Core - Standard Deviation
« Reply #6 on: November 01, 2010, 06:43:31 pm »
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You most likely counted the bar for 178 degress...I did too...
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Nads

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Re: Question 3 Core - Standard Deviation
« Reply #7 on: November 01, 2010, 07:06:33 pm »
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Y cant we do that though?
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LFTM

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Re: Question 3 Core - Standard Deviation
« Reply #8 on: November 01, 2010, 07:33:35 pm »
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Quote from: Nads on November 01, 2010, 07:06:33 pm
Y cant we do that though?

I did that wrong too.
It's because it says 179-181.
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xD_aQt

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Re: Question 3 Core - Standard Deviation
« Reply #9 on: November 01, 2010, 10:30:59 pm »
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:(
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summyx

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Re: Question 3 Core - Standard Deviation
« Reply #10 on: November 01, 2010, 10:57:31 pm »
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I don't think this question is fair on those who used the Essential Math book :/ because it clearly states that range / 4 = standard deviation.
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stonecold

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Re: Question 3 Core - Standard Deviation
« Reply #11 on: November 01, 2010, 10:58:30 pm »
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Quote from: summyx on November 01, 2010, 10:57:31 pm
I don't think this question is fair on those who used the Essential Math book :/ because it clearly states that range / 4 = standard deviation.

Hence why the essential book is a piece of shit for further maths...
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vidang

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Re: Question 3 Core - Standard Deviation
« Reply #12 on: November 01, 2010, 10:59:34 pm »
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thats an estimate though ^
clearly states "using the 68-95-99.7% rule"
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stonecold

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Re: Question 3 Core - Standard Deviation
« Reply #13 on: November 01, 2010, 11:02:41 pm »
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Quote from: vidang on November 01, 2010, 10:59:34 pm
thats an estimate though ^
clearly states "using the 68-95-99.7% rule"

shit estimate.  it should be range/7 really.
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summyx

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Re: Question 3 Core - Standard Deviation
« Reply #14 on: November 01, 2010, 11:10:09 pm »
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Quote from: vidang on November 01, 2010, 10:59:34 pm
thats an estimate though ^
clearly states "using the 68-95-99.7% rule"
Can you explain this formula to me? because under the "68-95-99.7% rule" in the Essentials book, all it talks about is the curves/mean/bottom percentages etc.

Oh and does anybody think vcaa will take this question into consideration when marking it?
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