Question 3 Core - Standard Deviation

[crayolé]

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?

VCAA knew that, they just wanted to you use it in a different way. Test if you really understood the concept. I very much doubt they'll accept C

[ZachCharge]

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.

What a load of crap, purposely creating a question a large group of students will get wrong simply due to the fact that they are lead to believe a certain formula should work with no real way of figuring out that said formula was wrong...

[LFTM]

But it said using that specific rule so you have to use the thing where there's 3 standard deviations on each side of the mean.
But yes i hate vcaa.

[kriptik]

They wont accept c because, there was a question like this in the 2001 exam and most people back then also did range/4. they didn't accept that answer. If they do accept it now it won't be fair for those in the past.

[seltick]

i just used the bell shape curve, as you had the upper quartile of 1.5 away from the mean, as SD1 is 34% not 25% you need to add a little extra to 1.5, then you end up with 2

[Streaker]

This is how I did it:

The fact that the boxplot was approximately symmetric or thereabouts, rendered the mean to be approximatelysimilar to the median (which could be easily determined). With this in mind, find the range of the boxplot (approximately 12). Split the range into six components (as there are six components in the bell-shaped curve which are the three standard deviations above and below the mean) and you get an answer of 2. The reason I split the range was because 99.7% is approximately equal to 100% (which accounts for all my data values).