Let x denote the number of missing pieces in a randomly selected 500-piece puzzle from a local thrift shop. The variable x has the following probability distribution: x=0, p(x)=0.33; x=1, p(x)=0.44; x=2, p(x)=0.2; x=3, p(x)=0.02; x=4, p(x)=0.01. Calculate and interpret σx.