Dot plots - mean and standard deviation

[Linked]

Quick question, how do you work out the mean and standard deviation of a dot plot? It was a question in the 2008 VCAA exam (question 5) - the answer is C and I put down B. I can't seem to find an example to help me anywhere...
I used Range/4 approximately equals SD, which gave me 1.3 - which obviously isnt the answer
But then did total values/number of values and got 2.1
What was I supposed to do next?

Please help me out!
Thank you

[chemkid_23]

was just about to ask this question
textbook says range/4 but apparently we have to do range/6

can anyone clear this up?

[abzzzz]

It's range/6 if it's approximately symmetric

[chemkid_23]

so when is it range/4?

[mazcox]

just enter it onto the spreadsheet on your calculator and do one variable stats.
so for this question enter
0
0
0
1
1
2
2
2
2
3
3
4
4
5

[mazcox]

personally i wouldnt worry about these "range/4" type rules, as the above method will always work

[chemkid_23]

what about qs3 core exam 1 2010

[mazcox]

yes, for that question i just saw that there was 6 degrees between the median and the maxX/minX points on the box plot.
so from that you can tell that the SD is 6/3 = 2 degrees

[chemkid_23]

yes, for that question i just saw that there was 6 degrees between the median and the maxX/minX points on the box plot.
so from that you can tell that the SD is 6/3 = 2 degrees

so im guessing that was using logic, and that there isnt a rule for that?

[mazcox]

yeah pretty much, but i suppose that is the "range/6" rule, because all i did was take HALF the range and divide it by 3 instead.
same dog different s**t
when it comes down to these sorts of questions on the exam, just remember they cant ask you anything that isnt on the study design.
just think about what you know and you'll get it.

[_avO]

yes, for that question i just saw that there was 6 degrees between the median and the maxX/minX points on the box plot.
so from that you can tell that the SD is 6/3 = 2 degrees

so im guessing that was using logic, and that there isnt a rule for that?

Actually for that question they asked you to use the 68-95-99.7% rule so you have to divide the range into 6 deviations

[Linked]

Thanks everyone! Started to freak out before - "WHY DON'T I KNOW THIS??"
All good now
Good luck for the exam!

[DannyN]

what about qs3 core exam 1 2010

nvm