# S1 helpWatch

#1
Hi,

I got an s1 exam tmoro and i need help on box plots.. i know how to draw them but i dont know how to analyse them.

How would you go about analysing a box plot?
How would you go about comparing 2 box plots?

Thanx
0

12 years ago
#2
Look at the skewness of the data (Q2-Q1 < Q3-Q2)
How 'tightly packed' is the middle 50%

When comparing look at things like differences in where the quartiles lie (Differences in IQR), the 2 different measures of skewness, any outliers and you may want to look at things such as the overall spread of the data.
0
12 years ago
#3
Just draw the two on the same diagram with the same scale- the examiners seem to like that approach. Other than that- everything is as Smidster mentioned.
0
#4
thanks alot clears things up
0
12 years ago
#5
hey i'd fort i shud tell u 1 more thing about box plots, wen it cums 2 outliers, dont include them, show them on thje box plot graph n label them, but dont use them as ur maximum, to work out a outlier it 1.5 (IQR), below the lower quartile n above the upper quartile, n if u have a outlier plot the value of the (1.5 x IQR) + the upper quartile
GUD LUCK FOR 2MORO, i got S1 n D1 2moro
0
12 years ago
#6
I think this is right; if the median is nearer Q3/75% mark then the data is negatively skewed, if its nearer Q1/25% mark then its positively skewed. If its in the middle then its a symmetrical/normal distribution.

So you can compare two by seeing whether one is negatively/positively skewed.
0
12 years ago
#7
There is a question about delay of aeroplanes in 2005 or 2006. Q1 is 12 and IQR is 24. So the boxplot will extend to -12 or 0 (since we are talking about delay)?
0
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