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VCE Stuff => VCE Mathematics => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE General & Further Mathematics => Topic started by: panicatthelunchbar on February 14, 2012, 10:37:15 pm

Title: Silly Q
Post by: panicatthelunchbar on February 14, 2012, 10:37:15 pm

When looking at box plots, how do you tell if its symmetrical or skewed? Getting confused :/

Thanks

Title: Re: Silly Q
Post by: Daenerys Targaryen on February 14, 2012, 10:48:55 pm

well you can kinda tell...
when its symetrical you have rather the same distribution at either side from the mean.
when its negatively skewed the data mostly lies on the right side and the 'tail' is facing the negative direction in terms of a number line
and positively skewed is when the data is mostly on the left hand side and the tail faces the positive direction (right)

Title: Re: Silly Q
Post by: Mariammm on February 14, 2012, 10:53:07 pm

Its exactly like a histogram
Symmetric boxplot: the median is generally in the middle of the box. So, if you measure either side of the median, they should be approximately the same in length. However, a simple observation can determine this - look at the boxplot and ask yourself: are both sides (divided by the median) equal?
If the answer is yes, it is symmetric
If the answer is no, it is skewed
It can be
Positively skewed: the median will be closer to the left end of the boxplot. The right end will be longer - 'gradually tailing off of data values to the right'
Negatively skewed: exact opposite of positively skewed
The median will be closer to the right end of the box plot, and the left whisker will be longer, tailing off in the left direction
I really hope that makes sense....

Title: Re: Silly Q
Post by: MagicGecko on March 31, 2012, 04:37:47 pm

i learn better with visual info...
http://www.google.com.au/imgres?q=negatively+skewed+box+plot&um=1&hl=en&sa=N&biw=1366&bih=627&tbm=isch&tbnid=ML24gRcMpBk6KM:&imgrefurl=http://mathsfm234.wordpress.com/2011/02/02/dot-plots/&docid=P1mheuaT4AKZsM&imgurl=http://mathsfm134.edublogs.org/files/2010/01/Picture-50.png&w=298&h=221&ei=fZZ2T7_MMsKImQWHoPzpDw&zoom=1&iact=rc&dur=125&sig=102828496790132042780&page=1&tbnh=135&tbnw=182&start=0&ndsp=19&ved=1t:429,r:8,s:0&tx=72&ty=74

this shows most of the are of the boxplot on the right hand side, also the median is located more on the left hand side. another way to

http://www.google.com.au/imgres?q=skewed+box+plot&um=1&hl=en&biw=1366&bih=627&tbm=isch&tbnid=jhGZ8Z4QwhNK4M:&imgrefurl=http://onlinecourses.science.psu.edu/stat800/book/export/html/6&docid=Y9rwKCS_VJvi1M&imgurl=https://onlinecourses.science.psu.edu/stat800/sites/onlinecourses.science.psu.edu.stat800/files/lesson01/left_skew.gif&w=414&h=196&ei=0JZ2T9nENOn1mAXp9JjpDw&zoom=1&iact=hc&vpx=271&vpy=314&dur=2080&hovh=154&hovw=327&tx=204&ty=61&sig=102828496790132042780&page=1&tbnh=85&tbnw=179&start=0&ndsp=18&ved=1t:429,r:7,s:0

everything is the exact oppostie of what i meantion with the positively skewed boxplot above

http://www.google.com.au/imgres?q=symmetric+box+plot&um=1&hl=en&sa=X&biw=1366&bih=627&tbm=isch&tbnid=PjeMtfiiR4cMpM:&imgrefurl=http://stat.psu.edu/~ajw13/stat500_su_res/notes/lesson02/lesson02_print.html&docid=gxpzT77W5gCpgM&imgurl=http://sites.stat.psu.edu/~ajw13/stat500_su_res/notes/lesson02/images/symmetrc.gif&w=391&h=232&ei=AZd2T63sBc7JmAWzoJnpDw&zoom=1&iact=hc&vpx=106&vpy=302&dur=1325&hovh=173&hovw=292&tx=195&ty=71&sig=102828496790132042780&page=1&tbnh=112&tbnw=188&start=0&ndsp=18&ved=1t:429,r:6,s:0

everything in the boxplot is centred (the median is in the middle) equal area on each side.

HOPE I HELPED !!! ;D