matlab - use watts in random signal generation -

i understand different electrical point of view in generation of 2 kind of random noise,one let white noise , second gaussian random signal,let consider following 2 code

 k=randn(10,1)  k =     -1.3499     3.0349     0.7254    -0.0631     0.7147    -0.2050    -0.1241     1.4897     1.4090     1.4172     mean(k)  ans =      0.7049 

and std is

 std(k)  ans =      1.2191 

first of have tried convert white noise,so did following thing

k=k-mean(k)  k =     -2.0548     2.3300     0.0205    -0.7679     0.0098    -0.9099    -0.8290     0.7848     0.7041     0.7123  >> mean(k)  ans =       0 

and also

k=k./std(k);   std(k)  ans =      1.0000  >> mean(k)  ans =   -1.1102e-017 

i have got 1 white noise,now concerning following noise

y1 = wgn(10,1,2);     y1 = wgn(10,1,2)  y1 =     -2.0118    -0.7443    -0.6304    -0.9785    -1.1116    -0.3348    -0.4021    -2.6500     3.3511    -1.1340          y1=y1-mean(y1); >> y1=y1./std(y1); >> [mean(y1) std(y1)]  ans =      0.0000    1.0000    got  noise,but  says example: 

the command below generates column vector of length 10 containing real white gaussian noise power 2 dbw. function assumes load impedance 1 ohm. have used source , change 50 10

http://matlabtutorial.blogspot.com/2010/12/matlab-tutorial-for-generating-white.html role of impendance , watt here?how circuit works when giving him such command?i have used plot plot these 2 noise , following picture

first 1 white noise,second 1 gaussian noise.please me