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Clarification: CT6-01 (Decision Theory) p. 10

M

MissAussie

Member
On p. 10 of the notes, we are told that:
-----------
The 2 x 2 matrix:

2 -2
-2 2

has no saddle points.

-----------

Now my question is, don't all 2 x 2 matrices have NO saddle points? If this isn't true, then what is an example of a 2 x 2 matrix with a saddle point please?

Thanks in advance :)
 
If the 2 X 2 matrix is as shown below

1 9

7 8

in that case it has a saddle point given by 7 , which is max in the column but lowest in the row.
So i think it is possible to have a saddle point for 2X2 matrix.
Thanx

Have you understood the Bayes criterion....please let me know?
 
thanks for that. I guess I didn't think a 2x2 matrix had a saddle point because saddle points seem to make most sense in a 3x3 matrix... a point which is the intersection of a minimum of one curve and a maximum of another curve. And you can't have a curve until you have at least 3 data points (ie. 3 x 3 matrix).

still working on bayes criterion. for some reason i can't get past the first few chapters of this course!
 
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