this is kind of hard to read, but i think i've got it
mean:
0*.1+1*.25+2*.35+3*.2+4*.1= 1.95
The second moment:
0²*.1+1²*.25+2²*.35+3²*.2+4²*.1= 5.05
the variance is the second moment minus the first moment squared (first moment is the mean) and then the standard deviation is the square root of the mean
