Skewness

[jsmith613]

1. The problem statement, all variables and given/known data
http://www.thestudentroom.co.uk/attachment.php?attachmentid=103146&d=1306479703

Look at question 3(d)
and the graph for question 3
how is this graph NEGATIVELY SKEWED


2. Relevant equations



3. The attempt at a solution
I know that a -ve skew has a tail in the low x-values but I find it difficult to see that here :(

(I am not sure what further attempt I can give, I have said everything I know about shapes of skewed curves I just cannot see why it is -ve. I was hoping someone could help me with this!)

[rollcast]

Look at the answer to part c, a = 5.

So the left tail is 3 units long and the right tail is 2 units long

[jsmith613]

Look at the answer to part c, a = 5.

So the left tail is 3 units long and the right tail is 2 units long

I always though the tail was a flat bit? how does the tail relate to the median / mode
is it as follows:
the mode is assumed to be the middle of the graph
if the a<x<mode is greater than mode<x<b for a graph a<x<b then it is negative skew
if a<x<mode is less than mode<x<b then the graph for a<x<b is +ive skew?

[rollcast]

Sorry I was in the wrong part of my book for the answer, ok not much help but my book says

Negative skew = Mean < Median < Mode.

Positive skew = Mean > Median > Mode.

[rollcast]

Then you can deduce that because the area of both sides of the mode is the same, then the mean will lie on the longer side.

[jsmith613]

oh I see
ok
thanks